I empathize with you, cause I do have an idea of how large boobs can lower one's self esteem. But if you are seriously considering breast reduction, I think you should choose carefully the plastic surgeon.
I would advise you to put into consideration where you reside, and then make enquiries about the surgeons that are located around your vicinity. Making a very careful selection, based on the past works of the surgeon, so that you don't have any complaints.
You could then ask for the best surgery options that would bring out the best result in you, but its better you ask first hand from the surgeon.
The price for a full breast reduction procedure ranges between $3000 and $10000, with an average of $6000
I wish you the best.
I'm not sure how it would go in the UK, but you have to set up an appointment with a plastic surgeon. Go in for a consultation and he or she can tell you everything that will happen, with how the procedure goes and what to expect. You can reduce your breast size to basically any size you want them to be. I'm surprised you don't have back pain with the size you say you are. good luck!