easy...I dont know why but I love giving london house hunting advice, so sorry 4 the essay. first of all, check this site
http://www.globrix.com , you can easily define search criteria, but most importantly you can view what you have searched for on a map, which is good for getting the right location. Also im sure i dont need to say but if you find a nice looking flat, use Google Street view to check out the area!
For eddie, as has already been said UCL has excellent links so really does not matter which side of london you are in. Its a fucking beautiful uni and really good one at that, so nice one mate! If you are based in the main campus area, you will be in west central. Basically you will not be able to afford Zone 1, so search for Zone 2 and outwards. You could live any side of london, but the northern hemisphere of west round to north round to east would be best. You could live SW as well (lots of UCL students live near my house!) South and south east would be the most tricky as you have to go through london to get there, so bike rides etc become that bit more tricky.
Some good (affordable) areas that I know and would recommend to check out.
WEST
Shepherds Bush - good transport links, only a few stops on central line. Some lively areas, bars, and not too far from notting hill which is nice. Also Kensal Green/ Kensal Green/ North Kensington are worth looking at nearby.
Hammersmith/ Ravenscourt Park - Hammersmith has its own little centre, is on balance quite safe and suburbial, lots of nice parks, near to the river, can be affordable. You would not want to go any further west than hammesmith however, would start to get long.
SOUTH-WEST
Fulham/ West Kensington - Really nice area, got their own selection of bars, very safe (relatively) really good transport links into london up the picadilly line. In fact, UCL is right on the picadilly, and its probably worth noting its significantly faster than a lot of lines, you can get from barons court to Russell Square (UCL) in 20 minutes flat.
Clapham/ Wandsworth - Clapham has a really good high street for your standard drinking bar crawl, and is really lively, lots of students and young homeowners, and loads of fuckin australians for some reason. A bit pricey in places but good searching could find somehwhere
SOUTH
Vauxhall - some good clubs here, and bars, but outside of the centre bit not too much going on. Close to a couple of good parks tho, and close to the river... could be pricey
Balham/ Stockwell/ Brixton - Quite close to clapham but pretty good area. Stockwell is a bit rougher as is Brixton but I personally really like them - brixton is excellent for drinking and clubbing. Balham is more residential but I know for a fact theres loads of nice flats here in an ok price range
NORTH
Holloway (and surrounding area) - Really easy to get to UCL and also to access dubstep clubbing in shoreditch/ farringdon/ central... lots of london met students here, holloway road is very lively, affordable in some places
Camden Town/ Kentish Town - Really close to UCL but can be quite pricey. Camden itself has amazing vibes, and good for shopping, clubbing and drinking, easily access everything on the northern line
NORTH EAST
Hackney/ Dalston / Stoke Newington/ Mile End/ Stepney - all amazing areas, close to shoreditch, its definitely the edgier side of london, lots of bass music, but also less safe then out west (nothing to worry about tho, on the whole students are fine) Some of those would be a little further away from UCL, ubt close to loads of good bars, pubs, shopping, brick lane shoreditch... mile end in particular would be do-able for Belalala, really interesting area.
For Belalala the same applies really, anywhere in zone 2 outwards, but its a bit more affordable south east. I had friends that went to both Camberwell and Goldsmiths, its an amazing vibrant area, a little bit dodgy in places but students are usually fine. Its also much more affordable to live close to the uni so might as well stick to east/ south east...
Elephant and Castle - Really close to central (its zone 1) but it honestly is a shit hole. Might get some nice flats around here but its about a 2/10 for safety and niceness.
Brockley - Really suburbial, nice pubs and easy links to goldsmiths, its has less of a central london feel, is affordable but still very quick into london. Really good value for money on flats here as its a bit further out.
New Cross/ New Cross Gate - loads of arts students round here, so pretty trendy and good vibes, and obviously on the doorstep of the uni. Probably your best choice, but a bit more expensive than other places
Mile End/ Stepney - as it is north of the river, a little bit futher from the uni, but closer to all the good shit in east central. You can get some really nice places here for quite affordable prices, and again is pretty lively (for both good and bad reasons)
Peckham - You might find some nice affordable places here, and its not too bad to be fair but i definitely wouldn't go out of my way to live there. London's worst area for gun/ knife crime (shouldnt put you off too much though, its only london afterall, and its 90% gang related, civillians with their head down are fine)
Dulwich/ East Dulwich - Definiately check these two out, especially East Dulwich....some really nice, safe streets here, and quite suburbial considering how close to everything it is.
Greenwich/ Deptford - Lots of jokes to be had in this area, very random high streets, bizarre folk wandering around. Has to be said though most of Deptford high street smells of fish 95% percent of the time. REally close to the river here too, which is alway nice. Any of the above areas, you can get some amazing views across london seeing The City/ Canary Wharf (fwiw)
Camberwell - really central, whilst being mainly a residential area, good transport links both into london and to the uni, definitely a decent area to live.
For all of the above, bear in mind theres not much London Underground (tube) here so you definitely need to check out the national rail network (mainline trains). Also, its good timing as the London Overground network is now in full effect meaning from New Cross/ Brockley/ Peckham you have a direct link up into east central and Shoreditch (london's best drinking area, home to FWD, rhythm factory and loads more!) check it here
http://www.tfl.gov.uk/corporate/project ... 15359.aspx
hope that is of some help