Forget about clinics in UK as a basis for anything related to UAE. This pre medical that they do, and what I was trying to say nicely, counts for, precisely, two tenths of nothing (I substituted nothing for the actual word I wanted to use but forum policies 😅).Â
Maybe I need to explain the background to you as you are unduly fixated on the UK healthcare and pre-medicals. Around 10-15 years ago, the pre-medical was just a paper filling exercise. I remember arriving in the UAE with a one page pre-medical form filled out by my GP and no tests. The medical itself was done in the UAE.  Now consider the fact that most of the workers in the UAE come from Pakistan, India, Phillipines etc........all places, where, Hepatitis and TB are endemic; it would stand to reason that back then, there were a lot of people marked as UNFIT (and keep in mind, at that time, there was no relaxation i.e. you have Hep B/C, you are gone.......now they don't test for Hep C and Hep B is fine except in six categories). Employers started a fuss as they had to deport a lot of workers at their own cost.  Out of all this, GAMCA arose........this was put together by ALL GCC countries to do unified testing in countries of origin (the major sources of workers.......and not all countries). The clinics in origin countries have to abide by strict protocols and if unfit people beyond a certain %age get through to the GCC (and caught in the medical there), their licenses can be revoked. Then there are non-Gamca countries like the UK where these diseases are not widespread enough and / or the amount of workers is not large enough to warrant an investment like Gamca . So they tell you to do it at any licensed healthcare facility. After all of this, GAMCA or non GAMCA, they will still DO a medical when you arrive which simply means that they don't rely on any other medical outside of the UAE. Why? because the purpose of that medical is to stop the flood or reduce it to a trickle, of unfit people coming which leads to higher deportation costs (or becoming illegal to avoid deportation), from high incidence / high volume countries ............which makes sense in the countries that I mentioned (as if you don't have something like GAMCA, people will pay for false results). Thus, the purpose is an additional layer of checks to reduce the volume........but the purpose is NOT reliance on these outside clinics. So don't ever assume that if GAMCA or whatever hospital has marked you as FIT.....then that means something. To the DHA, it means nothing.  Don't compare with Qatar........as far as I know, only Qatar and maybe Kuwait are the outliers i.e. reliance on GAMCA.....mainly because they don't have the infrastructure to handle the scale of in-country testing........every other GCC country relies on the in-country medical only.
A chest x-ray WILL be done in UAE as part of the normal visa medical and it is mandatory for all nationalities.  No special treatment to any nationality.Â
So simply stop worrying about the UK part of it - these clinics don't know anything, are not connected to the UAE authorities in any way and can neither harm nor help you in anything. Do what you have to do but more importantly, gather evidence (and attested like I described) for the real medical that will take place in the UAE.