I was just catching up on this thread and BigEndBob's post caught my eye:
Later we found out had descended and hit the Wrekin hill, tops 1400 feet, 30 feet from it's top. Local pilots know of it, but for someone unfamillier with the area, hard to see on a map. Looks like a Volcano.
In the late 60s, I was on a dual Chipmunk flight southeast of Shawbury, above a stratus layer. My instructor didn't want to wait for the AH to re-erect after some aerobatics, so he told me to descend through a very narrow hole in the cloud, with some green fields just visible below. When we reached cloud base, I was surprised to see we were directly over the top of the Wrekin, although safely above it. My instructor told me that it was a well known phenomenon - even a light wind blowing over the Shropshire Plain would lift the airmass over the Wrekin and cause local dissipation of the cloud. I hasten to add that this is not a trick I would recommend if the cloud base is below the hill tops.
This anecdote brings back one of the joys of RAF Chipmunk flying in the winter. We could take off on a typical, miserable winter's day with limited visibility and low cloud base, climb through a stratus layer, picking up a bit of ice on the way and then break out into blue sky, with the sun shining and a white cloud deck stretching as far as you could see. The instructors didn't like it so much, because the back seat was very drafty and cold as I discovered when doing instrument flying from the back seat.