What credits would you have been given under the old UK national licence system?
None at all.
I am in almost the same situation as who..., I have UK national CPL(A)/IR/FI/FE (8500 hrs) and ATPL(H)/IR/FI (3500 hrs) and have always understood that I would have to pass the appropriate exams, be they UK or JAA, in order to gain an ATPL(A). I guess that the difference is that I never saw the need to gain an ATPL(A) just to qualify as a glorified bus driver. I'm just having too much fun being a real pilot!