Gday all, managed to get it done. I took a bit of advice from all the different posts.
Connected the trailer to the tow bar. Jacked it up against some timber and a carpet tile against the hull around the middle. Once it was up, I put some timber and carpet tile further back towards the stern, and had a bit of structural timber at the front of the boat against the bow to hold it up. Then pulled the jack out (very, very carefully!)
It wasn’t pretty, but got the job done. I was able to get the fibreglassing, ship shape, and some top coat on before I had to lower it again - because I had to go to that place that funds my amateur boating and fishing…work.
The boat now looks like a beige rainbow, and I’ve got a lot of fairing and painting left to do, but it’s repaired and almost done.
Thanks again everyone for all the great advice