I recently replaced the roof of my shed (which is adjoined to the
house) with Clear UPVC roofing sheets. I used self adhesive flashing
tape along the edges with a brick wall. Since installing the roof I
have noticed a couple of major leaks, noticably where i have had to
cut the sheet for guttering etc. The leaks are not visible. I have
tried to put extra flashing tape but this does not seem to solve the
problem.

Is there anything else i can do to stop the leaks, is there any
subtance i can use to maybe paint on which will solidify and fill all
the little gaps ? im slightly worried as i have a freezer in the shed
and electric lighting etc.

Thanx in advance