I now think it might be better to ride from Mandalay to Yangon. I think the region around Mandalay is more touristy, so might be better to get started there. It will be 2 days to Bagan, and then we can have a “day off” to sight see round Bagan, and then head off south to Yangon….
Flights are a little tricky. You can’t fly direct to Burma from the UK. Best option looks to be a BA flight to Bangkok in Thailand, and then get a Bangkok Airways flight to Mandalay. We can then do the reverse trip from Yangon.