Never pay by Bank transfer unless you're 100% confident who you're dealing with. I was caught once for £2,500 when I thought I was dealing with a proper company. Turned out it was some scumbag masquerading as a legit business and a check at Company's House showed he'd made a career out of going bust owing God knows how many people money. I got his address but in the end decided I didn't want to get locked up.