Service area advice please M25 & M20

Quasar524

We will be travelling down soon from West Midlands to Dover, planning to go via M40, M25 and M20.

Last time we did this some 10 years ago I recall the only services once you hit the M25 were at Clacket Lane, which only had space for 2 or 3 units.  Does anyone know if the situation there has improved since then?

Also I note from a road atlas bought last year that a new service area was under construction near Cobham.  Is this open now, and if so does it provide better caravan parking than Clacket Lane?

Alternatively are there any better stops to be had by pulling off the motorway?  Not looking for restaurants orshops, just somewhere safe to stop and stretch our legs.