Hey
I also had this problem with my TB vaccination. I went through my GP first who referred me to a private clinic near me which was also £150 ... I got in touch with my local occupational health board and with a bit of haggling they eventually agreed to see me when I played on the fact that it was for my job. They were very reluctant to give it to me at first because they 'no longer provide TB vaccinations' but eventually they did. If that fails, your employer should pay for the vaccination privately because its a legal requirement... Hope you get it sorted soon!