£15 for posting an AEG really isn't that huge a deal. Granted I'm speaking from a position of a well paid job and no kids to suck all the fun out of my life money out of my account but even so. Yes, free postage was great but when you take into account how much cheaper they are selling the guns in the first place it's not so bad. They've potentially done it to try and cover the insurance claims of postage into the UK when customs get involved. They've had an "at your own risk" disclaimer on UK shipping for a while now.
As for emailing them and demanding free postage just because Gunfire do? Bit childish. It's their business they can charge whatever the hell they like. If you don't want to pay it, buy from someone else. Simple and more effective.