Hi SI,
Ah, Limewashing church buildings

Limewashing of churches was not uncommon in the medieval period, however by the 18th/19th century most had fallen off or had been removed.
The coating of the stonework could be one of three process (or a combination of them); to apply a limewash would be simply that. An application of limewash to the stonework. If the stonework was fairly rough or poor quality, a lime slurry (a thick limewash) could be applied to help fill gaps and prevent moisture ingress between the stones, or the third option for poor or undulating stonework would be to lime render to produce an even surface and then apply a limewash.
Coloured limewashes could also be applied. I have seen modern pink and ochre limewash applied to historic buildings. I suspect flint buildings (a bit out of my area) could have been lmewashed to reduce the washing out of the soft lime mortar from between the flint walling stone.
St leonards church in St leonards, Bucks (
http://en.wikipedia.org/wiki/St_Leonards,_Buckinghamshire) has recently been lime rendered and lime washed, although I think the underlying structure is mostly "clunch" stone, which is not particularly weather resistant. Drayton Beauchamp Church, also in Bucks (
http://en.wikipedia.org/wiki/Drayton_Beauchamp) is not rendered, but has limestone blocks in the flint walling to help tie the wall construction together.
Although modern, the limerender applied to the tower of The Leigh church in Gloucestershire

has been lined out to represent dressed stonework; the stone in this area being mostly small section blue lias. The scheme appears to be similar seen inside medieval churches elsewhere
I think I have probably introduced more problems than resolution, here

RMZ