Hi Steve, I've got a Swift Challenger and just replaced the shower tray on Saturday. One of those jobs that you dread doing but once you've finished you wonder what you were stressing about.
Ours was cracked round the waste outlet and I hunted for info on replacements and repairs before coming to the conclusion that a new one was the best option for us. I did the usual web search thing for prices and ended up getting one from G.R.P. Leisure, absolutely brilliant to deal with. The hardest part of the job was finding the screws fixing the toilet to the floor but apart from that it was really straight forward, took about 2 hours in total. I spent a bit of time making sure that the new one was supported properly underneath to stop flexing which was probably the cause of the original failure, just used left over insulating material from under laminate flooring, 3mm thick sheets which let me build it up gradually until I was happy that it was sitting properly.
I realise that this might not be your ideal solution but if you do give it a go and need any advice or moral support, give me a shout and I'll happily try to help, bearing in mind that I'm not an expert by any means. Its the sort of job that any confident and reasonably competent diyer should be able to tackle though.
All the best
Mr Wilson