Update on progress thus far:

I did find a garage willing to let me do the work there with a generator, and a private storage facility who were willing to let me do the work there with built in power.

unfortunately I've figured both aren't suitable - access to the garage is terrible and it's quite clearly been broken into before, had strong advice some a friend of mine that neighborhood it'd be robbed in no time. The storage facility is far worse, looked great on the surface, very accepting of my ideas, was about to sign contracts then found out by a coincidence that the company was dissolved and doesn't exist, but is being posed as one. Very concerning and I don't think the best idea.

Cambridge Hackspace is about an hour from me, so might be an option. They don't have the risk assessments in place for welding though so can't weld there.

As suggested, I may have to drop the metals from the plan. Realistically given the options I have had so far weren't suitable I think I may have to skip out on this event and join the next one near enough as things currently stand, but I'll keep an eye out for anything that looks suitable, and might start going to the hackspace anyway for a bit more machining practice.