cheers m8. i just wanted to see if i had a case before i contacted either of them.
do you think i should bother or not?
I guess it depends on what sort of a person you are.
Looking at it reasonably they have sent you a card that will do (if it is a 6970 reference PCB with a TFIII cooler on) what your old one did. TBH? I would be surprised if the Lightning, power stages and fancy PCB and all can overclock more than a regular PCB. The issue with overclocking a 6970 doesn't fall on the power stages unlike other Lightning models (480 for example).
The 6970 core is a poor clocker when compared to say, a GTX 480. That is just down to the cores on them and the fact AMD probably had to ramp them really high to get them competing with the 570.
So theoretically you don't need that huge PCB, only the cooler for quieter operation.
If you bought a 6970 and were happy with it and was going to keep it? then yes, being reasonable about it they have replaced it with a card that will easily do what the one you sent back did.
However, you do have a point about the PCB. If at any point OCUK used that PCB to their advantage then you could argue the toss. Mind you, I have to admit that taking that attitude would be rather unreasonable. I know the Lightning has a nice big PCB, but at the end of the day as I said it does nothing the stock one does not.
Personally speaking I would just be glad I have a working card tbh.