No credit card company is going to accept �6000 if they think that they can get �8000 plus interest.
They only offer to accept reduced 'full and final' payments in situations where they're making very little profit (or even a loss) from leaving the debt in place.
For example, I owe about �4500 on one of my cards and (because I'm unemployed, with occasional casual work) the lender has been accepting �15 to �20 per month (with no interest added to the loan) for ages. Since this doesn't leave them with any profit after inflation and inter-bank interest charges have been taken into account - in fact, it almost certainly means that they're losing money - they'd probably leap at the chance to receive a one-off payment of, say, �3500 (which they could then lend to someone else who could provide them with a profit).
However, I've only reached the position where the lender might accept a reduced payment
after the point where my credit worthiness became non-existent.
Chris
PS: There's a similar post here:
http://www.theanswerbank.co.uk/Business-and-Fi nance/Question631091.html