I found the cause of my deck cracking probs. The ply has pulled away slightly at the inside of the front beam (see attached photo) and as it flexes, it cracks the deck and lets in water. I was going to leave it till winter but I took on a fair bit of water in Saturdays "fresh" conditions so I thought I'd fix it before the states.
My thoughts are to use a syringe to get as much epoxy in as possible and then clamp, followed by a tidy up with some filler on the deck cracks. Will this do the job or is there a better method?