i just wanted to know the market prices of semi - deattached houses with 3 bedrooms in greystones ,s11 area.and also price for 2 bebrm falts.the average prices only.we wanted to buy one

Depends on what part - but 3 bed semis are generally between 200k and 230k.

If you log on to Upmystreet, and go into the property prices in you area, you will get a list of all the recent sales and prices of properties in you post code. It's a free service and really easy to use.:)