GBP 1600 per month is plenty, especially with £200k safety net. Look to live in Ekkamai or ONut if your in BKK, otherwise Hua Hin, Jomtien and Chang Mai are all reasonably priced too.
After coming through customs there are signs to the taxi rank, there are 2 channels one for a large taxi and one for a standard taxi, at the machine you press for a ticket and it gives you a ticket with the parking bay number on, go walk to your taxi, your driver awaits.
I hope she speaks English well as there will be language tests and a Life in the UK tests to come later on. The household must earn near on £39k too, new rules are coming soon.
Good luck, I'm on the last leg with my wife. It's worth it.