well back in my day it was a government grant so unfortunately I didn't deal with UK student loans, but second time around at uni a couple of years back there were students in transition and I don't think they had any problem.
What you have to do is the same as you will need to do with the university, that is send a letter to the company explaining the change of name and gender and enclose a CERTIFIED copy of the deed poll or statutory declaration document. A certified copy is a photocopy made by a solicitor and stamped with the solicitors official seal saying that it is a true and unaltered copy. Most organisations will insist on seeing either a cerified copy or the original document (NO! - NEVER SEND the original because they lose them).
The only problem you are likely to get is the overworked admin department in the student loans company who have a bit of an unfortunate reputation for a.) taking six years to do things and b.) making mistakes. I think you might find that a few follow up phone calls may be needed but it should be ok. They have seen it all before.
By the way you can change your name by either deed poll or statutory declaration. They are both drawn up and sworn in a solicitors office. My understanding is that the second method is theoretically easier in our situation because it requires no publication of the new names in a local newspaper, which technically I think a deed poll does.
Good thinking on timing though. Hvaing both my degrees and my "A" and "O" level certificates in my proper name has proved rather useful at times... Mind you since the gender recognition act there are now official mechanisms to get them all changed if necessary.
