Yes, you need a good quality primer. I haven't tried the Dulux one but I am a big fan of Zinsser products, which you can get from any decorators' merchants.
Zinsser BIN is one of the oldest and best primers out there. It sticks to pretty much everything. It dries in 15 minutes and is recoatable after 30, so it's super quick.
Another good one is Zinsser Bullseye 123 Plus. It's water based, so very easy to use and dries in 30 minutes.
Or there is Zinsser Coverstain, which is solvent based, but very good value and recoatable in 2 hours.
Avoid painting over any dirty, greasy or sticky areas. Clean the painted surfaces first with sugar soap or something similar, then allow to dry before priming.
If you're in a hurry, methylated spirits is a good pre-painting cleaner (also works wonders on upvc window frames).
Artex ceilings are best over-tacked with plasterboard and then skimmed. But if you don't have a good ceiling height, then they can be plastered over directly.
Good luck! I'm sure it will look great when it's all done.