The price of SSD in the UK is very good right now. There are often deal of the day type specials. ARIA, EBUYER, SCAN, OCUK and DABS to name a few.
As to best - well here is the thing, most of the SSD's are all using the same controller and buy their NAND from the same factory. Those that don't are all Samsung, Crucial, some Intel and some OCZ.
Right now get the biggest sized SSD that your budget can afford and enjoy. For me the 256GB Crucial M4 at £101 was a no brainier.
To help us help you - please provide as much information about your system and the problem as possible.