Am terrified of the dentist, always have been - deathly afraid, as in - gripping the arm rest, shaking, crying, severe anxiety . Have had some horrific experiences with cold, unsympathetic dentists when I was a child which scarred me for life basically. I haven't been to a dentist in 4 years

Teeth were generally ok until last year,(warning: tmi) a small hole formed in my lower left molar, I ignored it and it has decayed and decayed until part of the tooth has actually broken off, it is extremely painful, extremely sensitive - I can barely eat because moving my jaw hurts.
I have found out about something called dental sedation, and I would really love to just be knocked out and wake up with my teeth fixed.
Problem is, the price is sky high for where I live (London) I've been told £250 per hour
We can't afford that, but the only other alternative is suffering in extreme pain and possibly becoming a painkiller addict.
What can I do?
Please don't suggest going to a regular dentist, I can't, I really can't.