Thanks John, but I think I may not have explained myself properly.
The problem isn't with the hull & deck joint, I haven't reached that stage yet as the two are not joined, it is only with the full layer of glass that is epoxied onto the deck. It is now trimmed back from the sheer line by about 10mm. It is this raw edge that is lifting from the deck timber in places.
I will attempt to post a picture that I have just taken with my phone (it will probably be poor), my camera is not here.
Glen G.

: Hi Glen,
: It sounds like you didn't prepare the surface where you overlapped properly.
: You should wash, sand and wash again any epoxy you are going to epoxy over
: unless it is within the time that you can still get a chemical bond.

: What to do? Cut where the deck and hull fibreglass meet. Peel off the
: overlapping strip you just created. Wash, sand and wash a 2'strip, 1"
: either side of the seam right around the boat. Get some tight weave 4 oz
: glass, cut it into 2" strips on the diagonal and expoxy in place.
: Feather in when hard.
: It will come up fine.
: JohnK