David Hearn wrote:

Based on this - what preparation should I do before pasting/painting? I've
got 6L of Screwfix PVA bond which I think on the back says it can be diluted
4:1 to seal things like this. Is this okay, or could I dilute it a little
more? Is there something better to put on before papering/painting?

Yup, 4:1 PVA is exactly what you need. Use it liberally, and
apply to anything that looks remotely crumbly or porous.


Also - I've got a large area of plaster missing from a wall (it had all
blown from the blockwork) and I think I may need to put PVA onto this wall
as well before replastering (else all the water would be drawn out).
Should I just use the same dilution as I do on the other wall?

Yup, as above.

--
Grunff