I noted a comment in one of the threads about a single routing from Elstree through LCY to Lydd. That routing take3s you through the very busy area to the East of Biggin and then rather close to the West of Lashenden (falling bodies ets..).
If you route from Elstree to Detling then to Lydd, you will find the distance flown moreorless the same, and a lot safer (apart from the honey-pot at DET).