I did actually ask the university the same question as my own study plan also only has 50 points of level 1 subjects, not including UMEP (I really don't want to waste 25 points crediting those) but the university was so kind to say "we can't help you as you're not enrolled in the degree yet". Honestly, that part of university policy is ridiculous. As a result, I'm not too sure. My case is weird though, because as I plan on doing a maths diploma and as I'm eligible for Chancellors, I can get an entire diploma done for free, so I can move as many maths subjects as possible away from my BSc into my diploma to free up more space, so crediting UMEP isn't so much of a hassle for me.
One thing the university staff DID tell me, however, was that you'd need to credit 62.5 points of level 1 science subjects as that is the basic structure of the BSc. It's a dud rule and I'm not sure if you can get around it. Try talking to them; I know I will.
But yeah, I'm planning on doing 3 level 2 subjects next year. I'm hoping they let us.
Which MUEP did you do? If it was chemistry...the MUEP and UMEP chemistry courses are quite different. I don't know about the others though.