Here is the updated route (with added trip to Mt Popa and day at the beach at the end).
I’ve put clickable links to some of the places that we’ll stay.
Day 1 : Leave London (London -> Bangkok -> Mandalay)
Day 2 : Arrive Mandalay
Day 3 : Mandalay -> Myingyan (100km)
Day 4 : Myingyan -> Bagan (75km)
Day 5 : sight seeing in Bagan
Day 6 : Bagan -> Mt Popa -> Yenangyaung (130km)
Day 7 : Yenangyaung -> Taungdwingyi (110km)
Day 8 : Taungdwingyi -> Aunglan/Thayet (100km)
Will need to get boat over river from Aunglan to Thayet
Day 9 : Thayet -> Pyay (90km)
Day 10 : Pyay -> Myanaung (110km)
Day 11 : Myanaung -> Hinthada (110km)
Day 12 : Hinthada -> Nyaungdon (100km)
Day 13 : Nyaungdon -> Yangon -> Pub (80km)
Day 14 : Sightseeing in Yangon
Day 15 : Beach 🙂
Day 16 : Fly Yangon -> Bangkok -> London
Total : 950km + 50km faffing about getting lost = 1000km!!!