Hmmm, tricky. It may not be what you want to hear, but I would think it would be a lot easier to hire [rent] a "motorhome/motorcaravan" [RV] than hire a towcar and trailer.
Getting a towcar with a "towbar" [hitch] fitted isn't going to be easy, but it is certainly possible, though maybe not at a price you would like. Then hiring a "caravan" [trailer] isn't difficult. These are likely to be from separate companies, which creates its own problems.
Problem 1: you need the towcar insurance to cover the caravan too and even as an experienced tow-er from abroad, you may find this a problem.
Problem 2: there are restrictions in most European countries about what license
you need to tow a caravan, particularly for younger drivers. In some cases you need to pass an additional driving test to tow. Now how this applies to someone from abroad, I just don't know - and I'm sure sure who does.
If you drove your own towcar/trailer into any European country, then I believe your entitlement to drive/tow at home would be sufficient, but whether the hired towcar insurance company would see it that way, I doubt.
In Britain, it's only folk who had a driving license
issued before 1997 who are entitled to tow without a further test and since you don't have a British license
from back then, you may fall
into the 'younger driver' bracket, whatever your age.
If you hired a motorhome, it's likely that this would all be much easier as you wouldn't be trying to co-ordinate two separate hire companies from a few thousand miles away......
The alternative is to try to find a caravan rental company that can arrange the towcar hire as well - that way there's a fighting chance that when you arrive, the two hire companies will work together.