Peter wrote:
I have been given some 4mm acrylic of the type used for signs. Great I
thought I can use this for all sorts of things... that is until I tried to
cut it. How do you do it, I've tried a hacksaw and tenon saw, etc - it
either cracks or melts. Any suggestions welcome.

Hacksaw, with lots of coolant can work.
Copious amounts of water may be worth a try.