Congrats, and thanks for the details! Re: canceling your work permit, was that a requirement? I would have assumed whatever visa you have gets auto-canceled when you get the DTV, but in this case if you had been denied the DTV you'd have been stuck without the work permit, right?

Modest life in Bangkok but totally doable, *or* a very nice life in a smaller city with few expats if you're comfortable with that. (Think Buri Ram, not Hua Hin.) Or split the difference and go to Chiang Mai but then you've got poison air a few months a year. In any case I hope you like Thai food and/or cooking.

Don't touch your nest egg: it's not that much but you'll really need it if this doesn't work out and you have to go back to UK. Also: plan in advance for health insurance, for little things it's fine to pay as you go but you'll lose that nest egg real fast if you're hit by a moped and go to the private hospital uninsured.

As others have noted: watch out for the booze and the babes, either one can torpedo your budget before you realize what's happening. The good news is that with a little patience you can find a partner who carries her own weight (or his, whatever) and drinking like normal Thai people is actually pretty cheap. You just have to like highballs. :-)

Among all the other keen observations here, I will add that it's a great argument in favor of fripfrop or crocs, because maybe you'll need to hose off your footwear. :-)

You want to make it easy on the reviewer, so I think err on the side of extra documentation.

Trickier part may be proving income, right? You have clients but you don't have a tax return if you just started in April.

Did you have to mail in your passport? Or could you take it in person and pick it up when done?