Doctors
Use Doctor Sagoo at KL in Malaysia. From memory, his office is at the KLCC twin towers, 4th floor. Cost-wise he is one of the cheapest in the region, and you can stay overnight in KL for approx 120MY (1200 baht). Overnight stays in Singapore cost an arm and a leg!
You can find Sagoo's contact numbers on the UK CAA website under foreign AMEs. He also does NZ, OZ, US, and a number of other medicals.
Any sort of renewals in thailand for UK CAA or JAA are a nightmare! I have just returned to the cold and bleak UK for my licence renewals.
GBB - Are you flying in Thailand?