Right chaps. It's been 10 months and a good deal of rain, snow and -12 temperatures and my light issue still hasn't re-appeared. In my case the windscreen being removed and refitted again has solved this. The original relay which was buzzing enough to make the girlfriend want a Lexus is behaving as it should.
In summary, if you've had a new screen and have this problem it's worth getting them to remove, clean and refit as a small misalignment could be the cause here.
Hope it helps,
new666uk