The M23 was supposed to head further into London, which is why today it starts at a very messy J7.
In 1969, it was suggested that the new M23 would have services at Woodmansterne. However, little detail was established because the motorway was unlikely to be built "for many years". Another service area was considered near Shipley Bridge, but was ruled out for being too close to Woodmansterne.
Later on, Woodmansterne was considered again, and "about eight months" was spent arguing the case for it. It was decided it should seat 600-800 people. Once the completion of the M23 had been cancelled permanently, the planned services disappeared too.
Merstham and Hooley
Meanwhile, the consultant's report for the road (which again makes it clear that you can't plan service stations in much detail until you are sure exactly what roads are being built where) did make two recommendations:
The first is for a service station between Rockshaw Road and a housing estate in Merstham, which appears to be only a matter of yards before the M23/M25 interchange. Presumably, this would require modifying the junction so that the services could cater for two roads at once. One report cites "amenity grounds" as a reason to build at Clacket Lane instead.
It also suggests "a more pleasant site" in the valley between Merstham and Hooley. This could either be part of M23 J7, or on the road immediately north of this junction.
It is likely that these options were meant to be an alternative to Clacket Lane more than they were meant to serve the M23.
The investigations noted that facilities were also available on the A23 south of Crawley. In 1993, Pease Pottage joined them, serving the M23 at the same time.