I had UK PPL with about 500hrs when I got this daft idea that I should proceed enthusiastically towards the UK ATPL via the national exams before JAA made things woefully more difficult. Whether or not in fact JAA exams are more difficult is debatable, I suppose, and I am now immune from the need to find out.
I devoutly hope.
But I do not think that my previous experience made a lot of difference to the effort required to pass the exams. They are just bloody hard work. The earlier you start, the earlier you are likely to finish the resits !