I've written my letter to HSBC, using their e-message service on-line, requesting the £634.00 of charges they've enforced upon me in the last three years to be refunded. Although I didn't ask for any of the interest to be refunded, I did mention that the total of charges didn't include them and that I believe I'm also entitled to them.
I guess I just didn't want to push my luck, even if that money is mine.
After this, hopefully I can work on getting at least the interest on my managed loan back.
Thanks to everyone for all your help and I'll keep you all up to date as to my progress.
Dimitri