Do you need to be in a good school catchment?
S7, S10, S11 & S17 have all good schools and hence higher prices, they are also nice places to live.
You should be able to get a nice 4/5 bed detatched for your budget at the moment, not sure what the market will do next year, thats a whole new thread!
There's a nice house for sale across from me just to give you a guide (S7)
Move further out of these areas and you will get more for your money.