I Like the bucket plan, Mike,
I was going to just put the pipe in and do it eventually, but seeing as I've almost got all the kit here spending 20 quid or so on the heating element seems like a better plan. we have a pressure reducer on the incoming cold water, down ro around 3 bar, bypassing that should give me enough head to perform a meaningful experiment, just need to organise some shed time - maybe organise the shed too!
Cheers
Stef