Assalamu Alaikum wa Rahmatullah
i know of courses available at 110 pounds per level and theres 4 levels, but its over quite a bit of time. I need to get the number from my masjid though, also East Londons LMC does arabic courses i think.
Finally check out::
http://www.almadinacollege.co.uk/
about your parents:
Its important to do something your interested in and if you find it dull staying in uni and wish to pursue arabic fi-sabilillah (for the sake of Allaah) then just speak to your parents about it, if they really dont want you to give up on your studies then compromise... go uni and do arabic part time.
I hope you the best, Assalamu Alaikum wa Rahmatullah
remember jannah lies under the feet of your mother, and our prophet sallallahi alaihi wasallaam said may he be humbled to dust the one whos parents live to old age and he still cant get into jannah....