failing that route some truck yards, builders merchants have the scales. it sounds odd but i often go into a depot to collect sand and i'm weighed in and out, possibly not as accurate but just a thought.
My local tip has a weigh bridge - might be worth a punt?
I got my car weighed at the local council industrial waste disposal place. I expect their weighbridge has to be reasonably accurate as they use it to charge companies for disposing of stuff.
The local Ministry of Transport test centre will have weighing facilities. They also carry sound meters so can check decibel levels of exhausts etc. Very handy for track day regs!!