Rick Priestly, Andy Chambers et al never made any secret about where the inspirations of
40k came from. It's a melange of 80s Punk/anti-Thatcherism Britan, Dune, 2000AD, Michal Moorcock,
LoTR and numerous other influences, all cast into something of its own.
Some of these are more obvious than others (the Dune influences for instance), with the Sardakur as Space Marines, of warp travel and 'navigators', and of galaxy-spanning crumbling empires. You have the more subtle, underlying and satirical influence of 2000AD and the Judge Dredd setting as well, although that disappeared towards the tail-end of 1st edition when the
40k universe started taking itself more seriously.
What I will say is that the setting has evolved a lot since then (it's nothing like as derivative as it once was).
As an interesting side-point, as the
OP has in this case (disregarding the 'carbon copy' comment) it's funny that every now and again I'll come across a bit of sci-fi or fantasy literature which you can see may have been influential. Just reading To Die in Italbar, by Roger Zelazny, in which the main protagonist bears more than a passing resemblance to a priest of Nurgle or similar. I'd say almost certainly that one probably influenced Brian Ansell concerning that part of the Chaos pantheon (although the nature of the disease/healing is much more subtle than in the case of Fantasy/
40k)