Hey Alice,
I spoke to the chief today and he said the best thing you could do for the walls in the gallery is to skim plaster them. You need to seal them with a diluted PVA mix first, then use a board finish plaster.
I dont really have much free time these days, but we might be able to work something out. When does the current exhibition end? Are there any dead days between exhibitions? It will take a 1-2 days to do it.
Sorry I did not look up top last night, I will do it when I come in on Wednesday.
Tim