You write very well and many symptoms you are describing are textbook bipolar. True, you do not have them all but you have enough to go get checked out. Especially racing thoughts and not needing much sleep during the period of professional and artistic elevation.

Please do not self-medicate with alcohol which can only make things worse. Schedule an appointment, get a referral, do what is needed in UK to obtain access to a psychiatrist. Maybe track your moods before you get to see a psychiatrist.