That isn't an option with the NHS, your records follow you everywhere and anyone who needs them (and has the appropriate access levels) can access them, they are kept on a MASSIVE electronic database.
(This can be a gift or a curse, my current pdoc is has referred to dmy history going more than 10 years, 3 house moves to different corners of the county and about a dozen pdocs ago, very confusing when a stranger has a better knowledge of your history than you)

Unless of course your decide to register with a new GP under a false identity and re-enter the system that way, I suspect that involves a little more effort than its worth.

CALLY: I read somewhere that borderlines have a high dropout rate when it comes to their treatment, so that isn't the best option if you want this wiped from your records.

Psychiatrists working in the NHS are always part of a larger mental health team, who will have a manager of some description. This is the person you need to speak to if you feel you are being badly treated by members of their team, and tbh it really does sound like your being treated like crap.