Went into the LBS today and they confirmed the stretched chain and worn teeth were causing my chin skipping problems. I managed to get out before parting with any cash at all.
Manager recommended a Shimano SLX cassette as good for value / shifting/ longevity / weight , mixed with a 971 or 951 Sram chain.
I already have a Sram rear mech which is OK.
Merlin have the SLX cassette for £30 which seems amazing value as an XTR one is over £100, chains are about £15 – £17 depending on which one you buy.
Any wise words of wisdom before I click on add to basket?

Nope, good choice, the SLX cassette is significantly lighter than the PG950, won't eat your hub as badly either.

Fire away, no problems there.

Fine to mix and good choice of mix for good performance with out the huge spend!

£47.90 for the cassette and a 971 chain.

Ordered now , Many Thanks for the prompt and helpful replies.

Am going to give the LBS some work though, they can rebuild my Eggbeaters as one has about 4mm float and will probably self destruct miles from home.

Dez.- I might need your chain whip and lockring tool if mine does not re-appear in the near future.