Quite looking forward to this, we live on the flight line and with the exception of one year, we have been treated to exceptional show as they fly over Chelmsford. We always get a puff of smoke from teh Red Arrows too
From my photos of the last Queen's flypast this year, the Lancaster was here around 12:45 and flew at least 5 circuits above me till the first jets arrived at about 12:54, last jet (Arrows) cleared us around 13:00. There is often a lone hawk around 12:26 checking cloud level before the formation propper. Sometimes the BBMF planes have been known to form up with the flypast formation just outside the M25 for some other flypasts, similar for helicopters.
No guarantees any of this will be repeated - its a larger formation as well, but previous years (2016, 2017 and 2013) have had the first planes over here at 12:45 +/- 1 min or so and the red arrows clear of here for 13:00.
I always monitor flightradar24, callsign 'TARTN01' (the big Voyager) is usually present in a holding circuit off lowestoft and a good indicator of where they are on the route (sometimes the radar is slightly delayed though).
This tweet gives a good idea of what to look for: https://BANNED/CivMilAir/status/1005390579109416961
Quite excited already - going to try and get some blurred props for the first time, at around 1000 m altitude, most aircraft are within reach of my 300 on DX format and with a larger sensor this time, might have some more crop available....
Some good info here:
http://www.military-airshows.co.uk/press18/raf100flypast2018.htm