I have parked at Stanmore Station overnight, I think it was £1 for the whole weekend. Used tube to get into Central London whilst seeing a show. Really easy.
Maybe, if you ask permission from your local council, talk it through with them, they might allow it. :)
Yes. Some stores may have areas specifically for larger vehicles to park in so that they're not parked in the main parking lot.
No. Camping is not allowed at Beltzville. for PA State Park camping,
WalMart does. McDonalds doesn't.