is doging still a thing? and if so is there any going on in Northampton? thanks 

Northampton
A428 lay-by Brayfield, just outside Bedford – Active 24/7
Salcey Forest – Active 24/7

Just found an article about dogging in the UK and came across these locations for Northampton.

There are still small communities of hobbyists, you just need a way to link up with them, or go straight to the location, though it might be a bit weird. 

It was always super weird to me. Can't imagine myself in the position of making out with complete strangers. I guess i'm too cautious for that. It requires a full laid back personality.

Hence the saying 'to each their own'.