Royal Ordnance (or least the Royal Ordnance factories) and Sterling armaments didn't get along terribly well. This is largely because the former had a habit of stealing the work of the latter.
In the case of the L2A3 SMG, after its adoption, ROF blithely announced that they would be making it, and not Sterling. No mention of any partnership, or even royalties. In the end, Sterling sued them and won.
During production, ROF made a complete balls up of several minor hiccups which Sterling had long since solved, and being the arrogant gits that they were didn't even have the balls to ask Sterling for help.
In the late 70s and early 80s, history repeated itself with ROF Enfield essentially stealing the Armalite AR 18 action, which was being licence produced at Sterling, for the SA 80 project. They even had the cheek to arrange a visit to Sterling under false pretences to have a sneaky peek at what machines they were using. Again, they ran into problems which Sterling had already solved, and again didn't have the balls to ask for help -- the fact that this would then be a tacit admission that they had ripped off a design which Sterling had paid for the licence rights to probably also has something to do with this. Again, no partnership, no licensing, no royalties, no nothing.
Last Enfield - SA80: The Reluctant Rifle, Steve Raw, R.Blake Stevens, ISBN: 0889353034
AK56 magazine, December 2006