Help planning East to West route avoiding (to the south of) London

Clark_ee

I'm planning a ride from Broadstairs in East Kent to Ebbw Vale and want to totally avoid London. No problems getting to Maidstone/Tonbridge area from the start, and again from Reading area west to Wales. But does anybody have experience of cycle-friendly routes between these two approximate areas? I really want to avoid London and the 'burbs without adding on too many extra miles and although I can map something out, you can't beat road experience and knowledge.
Thanks