Afraid I don't really know what you mean by "dodgy planes" in Burma or where you heard they were old and not safe. I flew Air Bagan several times last year. All aircraft were modern ATR-72's and 42s. One flight I was on a Fokker 100. Most of the other airlines fly ATR-72s. Some of the aircraft are quite new others less so...just like the 20 year old 747s/737s/MD-80s some airlines fly quite safely. But ATR's are in service all over this region (and others) and are perfectly safe.

Also not sure I understand why you think getting a visa for Myanmar is difficult. I got mine in 10 business days from the Embassy in Washington. I would imagine their embassy in the UK works about the same. Or you can always go stand in line in Bangkok like lots of other people seem to do. Or arrange a visa on arrival. Likewise I got my Vietnam visa within a couple of weeks from their embassy. No trouble at all. Just fill out the form, pay the fee, attach the photos...