The major problem out there is that dealers (perhaps maybe not knowingly), are selling crap at premium prices. Not only that but some deactivations are absolute crap too. The Brens being sold by one large dealer have the worst deactivation job I've ever seen, unnecessary cuts and grinding.
Most of the British GPMGs being sold out there are actually ex Indian guns and not British L7s, they've been marked to cover their origins. Some of the .50 cal M2s for sale have had their original markings removed and marked as Interarms manufacture and are crap, Lee Enfields made from lots of parts, not even the same models. Made up guns sold as experimental or rare models, and there are people out there who fall for it!!
In my opinion, the best items on the market at the moment are coming from WWA, Rytons, Mike Priest and Saracen Exports.