There is a good chance that the paint bubbled because it was put on too thickly and it didn't adhere properly to the walls. I would rub it all down and any bare patches give a coat or two of watered down emulsion first, then give all the walls a mist or watered down coat of the finish paint then follow this with two coats of the finish emulsion and that should work. Unless there is a real problem with the walls I wouldn't use PVA as it can actually cause problems like bubbling. Below you will see a copy of an e-mail from Dulux sent a few years ago confirming this. I am not saying it shouldn't be used under any circumstances but should only be used if really needed.
This e-mail was received from Dulux about putting PVA in with the first coat of emulsion or applying to walls as a mist coat.
Thank you for your E-mail I can categorically confirm we DON'T recommend using PVA to seal new or bare plaster. This is because the PVA will seal any residual moisture on the plaster and may cause bubbling when it dries. This is also stated in the BS 6150 and our ICI site work instruction.
Hope this helps.
Omar Amjad, ICI Paints Technical Advice CentreICI Paints, Wexham Road, SLOUGH, Berkshire. SL2 5DSPhone: +44 (0) 870 242 1100Visit our web site at
http://www.duluxtrade.co.uk