I has a most pleasant stay at this recently renovated hotel in St James, London. The location is a few hundred meters from the Piccadilly Circus tube station (you can ride there straight from Heathrow, which costs only 4 pounds!) which again is close to both Soho and the Oxford street. Highly recommended if you want to stay in the middle of everything. Cons: you have to pay for Wi-Fi (silly at a hotel in this price range) and the frenchy personnel speaks...well...erm... English with a French accent.

I heard the rooms are quite pricy during weekdays (300-400 pounds) and cheap during weekends. I wouldn't know about that because I was on a trip with all expenses paid. But that's another story :)