Local here.
The Costa thing and Windhill B1kepark are entirely unconnected.
The Costa in Longleat is off the sustains route. It is a shame that Longleat have taken this view but fully understandable that they do not wish non-paying through traffic using the parks fee-paying customer facilities.
Windhill is much improved fron the old black canon trails. Massive work has gone into them and it is now a pay and play Park. Brilliant and worth a visit. Outside of Windhill and the safari Park there are still many many trails around the forest free to ride.
For sustenance as stated above the Bath Arms in Crockerton, the other Bath Arms in Horningsham, and the Shearwater cafe are all excellent stops.
Ps, Windhill carpark is half a mile ride (if that) on a concrete road from the trailhead. Not “miles” as stated above.