Who replaces HD to SSD?

Hi guys, I know a *really* odd question...

I want to replace the HD on my early 2009 iMac to an SSD. I absolutely want to keep this - i do not want to buy a new iMac, even if it works out as better. What shops in the UK are capable of doing this lol - I wont do it myself and i have no idea who would do this!

Thanks :)