The riding's good, come on in!
The LCC is worth joining, as it's 20 quid a year and will get you a discount at most bike shops. They also produce a series of 20 or so maps that show cycle paths and quiet back streets.
If you're going to SOAS, you'll probably end up living around King's Cross or the Archway/Camden/Tufnell Park. None are particularly attractive, but there's lots going on. I used to live in Barnsbury, which is right by KX, and very nice. Good Japanese around SOAS - Ikkyu on Tottenham Court Rd, next door to the Scientologists, and Abeno for okonomiyaki on Museum St.
The roads in the West End tend to be wider and more one-wayish than in the City, but unless you're messengering, you probably won't end up in the square mile often. The surfaces are uniformly awful and covered in crud, so you'll want kevlar tyres.
Good bike shops are Mosquito, On Your Bike, Brixton Cycles. Avoid Evans, they blow goats like there's no tomorrow.