In most of his novels Robert neill is quite precise in the location of his story, but, surprisingly, he does not give the name of village where the Mallinders live and the action takes place - neither a real name nor a fictional one. He does however give some general hints: it is in Lancashire, and at the foot of the Pennines. That covers a lot of ground.
We do have some closer hints.
1. It is 8 miles from Garstang which is on the old road to the north (the A6, Preston to Lancaster).
2. He also tells us that the closest approach to the North road is 7 miles.
3. We also know there is a "Preston Road" from the village.
4. We also know there is an old water mill about a mile from the village towards the mountains.
5. Nearby (3 miles away, but clearly visible) there is a high peak (for the witchfire)
Let's see what we can do with these hints.
The foothills of the Pennines tells us that the village must be on the east side of the road to the north, and an eastern arc of 8 miles radius from Garstang passes through the village of Chipping and misses Longridge by about a mile. There are no other villages on this arc.
The closest approach to the road to the north is at Brock, 7 miles away. This makes Lonridge unlikely at less than 5 miles from Preston, and Longridge is hardly in the Pennine foothills.
There is a direct and old road to Preston from Chipping (through Longridge).
The distance from Chipping to Brock is 7 miles.
A prominent peak, Parlick Pike, is 3 miles from Chipping, and has a history of fires and beacons possibly originating from the Danish Massacre of 1002, and commemorated by signal fires lit on Parlick Pike, also on nearby Beacon Fell, Longridge Fell, and Pendle. The fires still observed in the nineteenth century on May 1st, Midsummer Day, August 31st, and November 1st. It has been suggested that these were feasts of sun or fire worship, and originated in re-Christian times. The custom re-surfaced (on Pendle at least) in the year 2000 celebrations.
On nearby Pendle the fires were known as Beltein or Beltan Fires (fires of Baal) as late as the nineteenth century. Tan is an old celtic name for fire.
There is an old water mill (Wolfen Mill) one mile from Chipping up Chipping Brook towards the dominant peak of Parlick Pike
There is old hall (Leagram Hall) just outside Chipping (half a mile) dating back to the Domesday Survey. This would fit well with the home of Sir John.
On the evidence above that the location of Chipping, Leagram Hall, and Wolfen Mill agree very well with the descriptionss of the locality in Witchfire at Lammas, I conclude that Neill had Chipping in mind when he wrote the novel.