Apply for different course while at uni

I’m studying psychology at cardiff uni but it’s **** and i want to study computer science instead (after some very careful consideration of course), could i apply for comp sci courses through ucas and still finish my first year of psych (i know there’s technically no point but i would like to for my own sanity), and then drop out of the psych course to start the comp sci one next september? and would i still be able to cover the first year of the new course with student finance?