Hi, I have been reccomended the CHV vaccine however have been told different times to give it, one vet says 7 days BEFORE mating another says 10 DAYS after mating

and then again 7-10days before whelping if bitch has taken.

Anyone else used it?

The datasheet says two 1ml doses should be given:
First injection: Either during heat or 7 - 10 days after the presumed date of mating.
Second injection: 1 to 2 weeks before the expected date of whelping.

Both your vets were right!

and based on that I'd go for after mating, as you could end up with no mating.