Hi Pete.
Sorry i missed this post, but the customer still has the car i showed her how to regen on the road when the light comes on,has regular oil changes now and lasts longer between needing regen.so lives with it.
In the last 2 years have had a few not only renaults,but other makes and normally find egr block,or stick slightly which causes the problem.so more services or at least a flush and oil change seem to help.
hth john.