Thanks for your reply Mark. I was advised by RS to use clear gelcoat with white pigment on the bottom of the board, and without pigment to replace a small section of the black carbon trailing edge, where I suppose the slight pink tinge isn't obvious.
I was in Cornwall all of last week, so picked up some white gelcoat repair in the chandlery in Penryn whilst I was there. I'll give it a go with the gelcoat repair and will see how that holds, if not I may well take you up on your kind offer of a bit from your tin!