I took the fork off over the weekend and as ramzilla suspected its a made in Taiwan replacement made by Lung. The headset had some plastic pieces too but both the headset and fork look newer than the frame. Could it be the frame is a made in taiwan too ? maybe that would explain the odd dropout ends and mismatched lugs on the bottom bracket and top tube ?
I'm going to carry on stripping the paint off and will post some more picks, I haven't come across anything on the net yet that looks similar, I'm discounting the Hobbs angle they look a very different build, although I guess the X prefix frame number could mean for export just some other company ?
One other thing I noticed was on the mudguard bar behind the bottom bracket there was a bit of electricians tape wrapped around. I thought taking this off might reveal something nasty and rusty but it was ok, its just there to cover a hole for attaching the mudguard which could get full of gunk, this is a weird fitting to me on most bikes this bit is a solid tube isn't it ?