Turns out that the 1kg bottle I've got should be alright for my needs- the thread isn't as odd as I feared like most these threads are! So I am just after a screw valve with m25 thread. Happy to pay for it or trade my valve or any of the bottles I mentioned (other than the 1kg one) also got other spares I could potentially trade so if you have a valve and have something in mind you want for it just let me know!
I know this should be in wanted section but I doubt anyone wants me to post same thread in wanted section.