Have been told to apply PVA mix 3 times Mon, Wed, Fri before he plasters on Saturday, is this normal practice as the house is fairly old? And what mix should be used?

PVA 3 times? Shouldn't need to do any more than twice on any background and you should always plaster onto PVA when it's tacky anyway as Brian has said. As for Daves suggestion then yes you could use Thistle Bond-it but i use Febond Blue-grit as it's half the price of Thistle. Using these will also give the background a better 'key' for the plaster as well,especially if they are low suction/painted walls. I would certainly question your 'plasterers' advice though. Carl.

I wound'nt use PVA as theres a better product on the Market. Thistle Bond-it. made by British Gypsum, you only need to apply this 24hrs before a re-skim and only apply once. Its green in colour so you can see where you have been. Dave DJB Plastering Ltd

Mix about 4/5 to 1 pva, one coat about 24hr before plastering and 2nd coat just before plastering, wait for it to go tacky. Add some food dye to see where you have covered.

bloody plasterer should be doing that anyway after all your paying him ??? 5:1 for dry walls let it go off 40 mins max then 3:1 before mixing up it with my dad did it and the way i do it ;)