After knocking down a (relatively recent) wall in my 17th C cottage, I have discovered that underneath the Artex-type ceiling is an old lath and plaster ceiling that is probably 18th or 19th C. Also, the walls had been covered in a kind of rough plasterwork which seems to be a similar material to the ceiling. Underneath is a mixture of old lime plaster (fairly solid) and cement etc where alterations have been done. After removing some test areas of paint, I have found that the Artex/plaster is easily removed with water and a sponge or scraper as it becomes soft and putty-like when wet, so the old plaster is easily exposed. My concern is that I do not know what the new plaster/Artex is (but I do know it was done in the late 1970's) or if it contains asbestos; I do know that it has lime in it as it fizzes in vinegar. Any suggestions? Most people I have spoken to (builders etc) advise me to leave it alone as the ceiling and plasterwork might not be very good anyway - and if I want a smooth ceiling, they say I should just counterbatten plasterboard onto the old one.