As I have not been back to the UK for 25 years, I cannot comment on the ones there, but in Australia, it is one of the most popular foods going around.
Although in my town in the UK where I come from (Harpenden) there are now two Thai places operating, I would imagine that the more people come out to Thailand, the more demand there will be to have them, and you will see them popping up all over the place.
Only problem I find, is that like most of the places I went to in HH (and other major resorts), they seem to lack a lot of the hotness that you get in places that are not so commercialised.
I have been to Ao Nang, Krabi, Koh Lanta, Phuket, Phi Phi Island and Koh Samui, and only on Koh Lanta did I sample anything like what I imagined Thailand food to be like in relation to its hotness without having to request it.
In HH, all of the resteraunts that are on the streets around the Hilton were very tourist type Thai food, but did find the ones in Poolsuk Road (by the temple) to be very good and the nearest thing to what I imagine local Thai food to taste like. I was there only a few weeks ago and were the only places that I ate when I wanted Thai food.
In Australia, there are loads of very small and medium size places popping up all over the place, but there are also some very good upmarket ones in most of the capital cities (in particular Sydney, Melbourne & Perth). You tend to pay a lot of money for the food there, but the ones that I have been to, you could not fault the quality of the food.
Who knows, if Thai Food gets to be that popular, it may remove some of the horrendous Chinese take aways that seem to have taken over every street corner in the UK.

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