I have a blue screen iMac.tried alt key. On start and command r. Tried unpleasant Nothing worked Helpl

Tried unpleasant

I can't help asking. What did you try that was unpleasant?

see here iMac (27-inch): AMD Radeon 6970M Video Card Replacement Program - Apple Support

Book yourself a genius appointment, and they will honour this replacement free of charge for up to 6 years due to consumer law.

You posted a link to a European site and program; the US repair/replacement programs do not include this video card program:

https://www.apple.com/support/exchange_repair/

Also, warranties in the US are either 1 year for a standard warranty and these programs are generally only for 3 years maximum; we do not have the same consumer laws as you do in the UK.

@nedevans:

If you book an appointment at the Genius Bar, the diagnostic/troubleshooting will be free of charge and they will be able to tell you what, if anything needs a repair or replacement; if there is no program and you are out of warranty, you would have to pay.