I just put together the Airfix counterpart. I have the Heller kit as well, but the Irish don't have the roof sight, so I used the Airfix one. As near as I can tell from a comparison, the one is pretty much a re-issue of the other, just with a different roof piece.
I found the fit atrocious, but I guess it's to be expected with an old kit. Of course, the worst of it is around the windows. <sigh>. Worse, the damned thing's a tail-sitter, which I didn't cop on until after I had the fuselage put together and sanded. Going to have to glue it to something. The turbine area threw me as well: I couldn't find a really good way to get the kit to look right, so I ended up just filling the lot up. Not many people will know the difference, and frankly, this isn't exactly going to be a competition-winner anyway.
I basically got sick of it, and am looking forward to something easier. Like a scratchbuild/conversion.
NTM