This is Dr. David
I am sorry you have back pain.
you need to go to the ER or the A&E and see a doctor there.
you may or may not be able to see an orthopedic specialist at the hospital. it depends on the hospital and who they have on call
the A&E doctors are well aware of back issues
you could very well have a slipped disk in your back pressing on nerves in your back causing pain.
you need an xray or CT or better yet an MRI scan of your back, but it can be very difficult to get a spine MRI scan in the UK.
the A&E can give you steroids to help decrease swelling to help the disk go back into place and pain medications to help decrease the pain.
let me know if you have questions.