I personally prefer the 7" tablets to the 10" as the 7" are much more portable and easier to hold with one hand.
I know you are asking about 10" tablets but I just purchased a Samsung Galaxy 2 7.0 tablet for US $250 (approx £160) and really like it. There is a 10" version of the same tablet that is above your stated price range (US$400, £257). My tablet has the latest Android 4.0 OS (Ice Cream Sandwich), has front and rear facing cameras, wifi, Bluetooth, GPS, 1G of RAM, 8G built-in storage and a SD card slot to add another 32G.
What features are you looking for in a tablet? What do you plan to use it for?