Thank you for your replies.
So it looks like polyester is the way to go.
I have watched a number of videos (youtube) and read a number of articles regarding fibreglass work and resins.
So would I be about right with the following process?
1) Do a soap test to spot leaks (Guess this may not be necessary if doing a complete bottom job but no harm)
2) Sand off the old filler and coarsely sand for (keying) the remaining good working area.
3) Clean thoroughly with acetone.
4) Wet in fiber glass strips with Polyester laminating resin (the stuff that does not cure completely) waiting for each layer to become tacky, building up the bottoms. How many layers is generally required for this process?
5) Wait for last layer to become tacky, it wont cure completely in air. (maybe use a polyester finishing resin)
6) Apply a gel coat to seal and thus cure and harden the underlying resin.
7) Progressively sand to a nice finish and polish.
I have just read the West System literature and this states that epoxy is far superior and may be used on polyester fibreglass hulls.
Indeed a number of other articles are recommending this too. Some quoting epoxy resin superior strength something like 2000psi as opposed to 200 for polyester and that it requires less prep work etc.
My head is buzzing and it hurts