Accidentally applied for a masters

Applied for Mcomp instead of Bsc for computer science 2025 1st yr entry but I don’t think I want to do a masters, should I do anything about it or just leave it? The application has already been sent off and received by the university

Contact the university, explain the mistake, and ask them to switch your application to your intended course.

I head you can switch when there - surely it's easier to do that

You're right, you can normally switch from BSc Computer Science to MComp Computer Science once you're there. Which uni are we talking about about?
My concern would be that the MSc course might have higher grade requirements, or might be more in demand. Either of those could reduce your chance of an offer. Also, on A level results day, the universities ability to be flexible with grades might vary between the two courses. So it just seems to make sense to apply for the course you actually want.
For example, at Aberystwyth University (alphabetically first in the search I did!), they're looking for BBB-CCC to join BSc Computer Science but AAA-AAB to join MComp Computer Science. Other universities may have similar (although likely less extreme) differences in entry requirements.

You're right, you can normally switch from BSc Computer Science to MComp Computer Science once you're there. Which uni are we talking about about?
My concern would be that the MSc course might have higher grade requirements, or might be more in demand. Either of those could reduce your chance of an offer. Also, on A level results day, the universities ability to be flexible with grades might vary between the two courses. So it just seems to make sense to apply for the course you actually want.
For example, at Aberystwyth University (alphabetically first in the search I did!), they're looking for BBB-CCC to join BSc Computer Science but AAA-AAB to join MComp Computer Science. Other universities may have similar (although likely less extreme) differences in entry requirements.

Sheffield, because I do cs and fm the offer should be AAB (predicted 3A* A) so not too worried about my grades but Sheffield is kinda my safest option so I don’t want to be rejected hahaha

The Sheffield website says the same thing for the entry requirements for bsc and mcomp for cs