Whilst trawling around the interwebs I've found some other groups using the term 'Roguemunda' to describe a hybrid of Necromunda and Rogue Trader rules they've cobbled together to use in their games. I guess there's something about the two rules sets that just do it for poeple like us! Whilst our own group tends to freestyle things by mutual consent, other groups have actually got around to setting their ideas down so others can use them too.
Here's a great example, and oddly, they do something which our own group has considered, which is taking the 'Logan's World' background from the Rogue Trader rulebook and using it as their own setting.
If anyone else wants to post links to their own, similar efforts here then please feel free to comment, with your links.
Keep up the good work everyone :-)