Hope this is allowed, but further to my WHYDTYCT post I just wanted to recommend and pass on the details of Ed at Elite Motorsport Engineering.   He's a great guy to deal with and runs a team of Ginettas, generating a lot of part-worn 195/50/15 PS3s every month!  He's selling them on eBay at £80/set plus £20 post, but is more than happy to do deals for bundles; if you contact him direct then single sets are £70, two for £130 and three for £180.  All plus post at £20/set if required.   Like I say, he's a good guy and spent time with me ragging out the water on 12 tyres (as I handpicked them from a huge stack) before they went in my car.   You can contact him on 07590804865.