I changed uni courses 3 times!
First uni I went to I hated my course, realised that within the first month. I had made a mistake, wasn't right for me, wasn't the course I thought it was. Decided to get to the end of the first term and review my options. Still hated it. Then came the problem of what I should change to if I quit that course. I had wanted to be a primary school teacher and was going to do a normal degree than a PCGE but decided that as I knew what I wanted to do I would rather go straight into a BAed English degree (4 year course, teaching and English). The problem was my uni wasn't very good for teaching and only offered limited teaching degrees. So changing course meant changing uni's. Took me another 6-8 weeks to do the research of where I wanted to go and sum up the courage to tell my parents!! I then simply contacted the tutor at the other uni and was honest with him. Told him I had always wanted to teach, didn't like the uni course I was on and asked if he would consider taking me. Got invited to interview and got offered a place, no UCAS involved!
Absolutely loved my BAed, best decision I made. Now I was unlucky that in my second term of my first year on my BAed I got ill and missed teaching practice and many lectures (have a history of suffering from ME). I talked to my tutor and we decided that I had either one or 2 choices. Firstly, forget this academic year and just get well, as my health was still too bad to cope with all the work and re-start again the next year. Or swap to a normal BA with fewer contact hours a week (7 instead of 14 + teaching practice) so a higher chance I could manage my health and the course, then do the PGCE. Decided as I had already had to do 2 first years that I couldn't face doing it again so would try to see if another course would take me 2/3 of the way through the academic year. If I couldn't get a place without restarting I would obviously stay on the BAed but if someone would admit me straight into year 2 then I would swap courses. Went for interview with tutor in another department who agreed that if I could pass the first year exam and write 2 suitable standard essays he would except me into the second year. Needless to say I passed and was excepted straight into year 2!
So, basically my point is that it is very easy to change courses, as long as you can prove your not changing because you are failing and you have good enough grades to be excepted by another faculty. You might need to prove to them commitment and ability but if they decide to accept you its very easy to change.
Additionally, doing a course you hate makes it twice as hard. Degrees require independant study and academic interest. If you hate a subject, finding the motivation can be very hard. I would rather spend an extra year at uni, do a degree I enjoy and get a good degree than struggle with a degree I hate, finish a year earlier but end up with a poor degree because my heart was never in it in the first place!