Is Turweston too far west? It's less far north than Peterborough and near to fast roads (M40 then A43). It really depends whether your North London is near the M11, the A1 or the M40.
If Turweston were any use to you, we have room in our AA-5 there. We relocated it from Cranfield (because Cranfield had become just too badly run while Turweston is excellently run. If I want lights or an IAP, I pop over to Oxford). The reasons for having space are that Turweston did not work for everyone geographically plus we did have one member lose their husband and with it their enthusiasm for flying.
Details here:
https://forums.flyer.co.uk/viewtopic.php?f=3&t=106939
I have been a member for two and a half years, have taken it to all sorts of places, including Poland. Just today, we are back from a night at Perranporth.