There's a photo of the lions on Rex Harris's Flickr page. Wherever we go, he seems to have got there before us.
Since our visit I read on the British History website that there was another tympanum:
"A second more elaborate tympanum, said to have come from the south wall, is at Cherington Park."
Mmm more elaborate. But I can't find a picture of it on the internet (yet). Wasn't it great when you could just stroll off with a tympanum and stick it on your own grand house. Cherington Park's just next door to the church. Perhaps I should have just gone and rang the bell. Maybe it was moved when Mr Baldwin repaired the church in 1815 and saw fit to carve his own name on the lintel below below the lions. Tch.
A slight Cherington update (8.8.14)I noticed on British Listed Buildings that the other tympanum was still on Cherington Park in the 1980s, despite the building's 'partial demolishment' in the 1950s. So this is good news for tympanum fans. (All two of us.)
I've also found out what the tympanum depicts, thanks to my lovely InterLibraryLoan of Charles Keyser's 1927 book. He says: "On upper part a sundial with serpent above, a lion on left, and griffin on right. Below four courses of the fish scale ornament, and three rows of indented on the lintel." He also says 'Probably moved in 1816', so perhaps he had the same idea as me about it being appropriated when the church was repaired. It sounds as if it is an interesting design.