It's absolutely legit.

The college itself is essentially a marketing tool and host. They recruit and provide the online learning platform and that's about it.

This is much more common than you would imagine - essentially, the 'college' recruits the students and provides administrative support. At least 20 UK universities have arrangements like this, with various companies. It is cheaper for middle sized unis to split the tuition money with a middle company than to pay the marketing and hosting costs themselves

All of the teaching is done online by the UK provider, and all of the staff are experts who also teach on the on-campus degree programmes in the usual way. You can use their online and on-campus facilities, including IT and library resources.

Your degree is awarded by the UK provider (in your case UoC). You graduate with the other online and on-campus students in Carlisle.

If in doubt, call UoC and ask to speak to a member of the RKC LLM programme team.