This page refers to several services which have been proposed on the M4 between J8/9 and J10.
The first was Warren Copse, which looked likely to go ahead for quite a while when it was first put forward in the early-'70s. However, it was unpopular with local residents who argued that the area is environmentally sensitive and that these services would be too far from Membury. Eventually the plans were dropped and the government started looking at other sites.
As part of a review of services to the west of the M25, the subject of services here came back in the late '90s. This time the two main sites were at Great Hazes and Great Wood, both roughly in the same location as Warren Copse. Great Wood would have been for westbound traffic only, possibly pairing up with an eastbound only site at Maidenhead.
They were all rejected and went to appeal and a public inquiry, but in the end it was decided that just Cobham on the M25 would be the best place for a service area.
It looks like all of the plans for Great Hazes and Great Wood were put forward by Extra. The biggest difference between the 1970s and the 1990s plans were that since then Reading services had opened 12 miles to the west.