Hi I recently removed a soil pipe that went down the back of the house and
through the extension (don't ask it was already there). It's left me with a
gaping hole in the flat roof of the extension. I patched it up with some
roofing felt and a bitchumin based mastic.

Is there an easy way to do a "proper" repair without getting the whole lot
re-roofed?

Cheers
J