First of all, welcome to the bipolar club
Are you a member of the MDF (Bipolar organisation)?- they're a fab charity (I think) that help those of us with BP. The website is at
MDF > Home . Membership is about £20 a year (less if you're unwaged) and gives you access to a really good employment law helpline. The forum on the website is really helpful too.
And yes, you are considered as disabled under the terms of the Disability Discrimination Act and therefore your employer needs to tread very carefully in terms of what they do and how they treat you...The Disability Rights Commission is another good place to look for assistance.
Hope that everything goes OK for you. I've been diagnosed now for five years (?) and have been in full time employment since. I'm now in a supervisory role with a very supportive employer - so it can be done!