Sorry, haven't done it myself. It can be cheaper to go abroad, and you can get some excellent dentistry, but the problem is any ongoing work will (probably) also need to be done there. You may be able to get private dentists to do subsequent work here, but sometimes the materials used are very different to those used in the UK.
I think a lot depends on the state of your teeth to being with, how intensive (and invasive) the work is, your general health and how much money you have to take care of anything that needs correction. Even some private work in the UK can sometimes need correction on subsequent visits.