A very simple question - but I have no experience of doing this ever. I
need to create a 4" diameter hole in an outside block built cavity wall for
a ventilation outlet. What is the best way to do this? Is there something
I can hire that would make it very quick and easy?

Also I need to cit a similar hole in a plasterboard ceiling - I presume this
is dead easy - best to use a jigsaw?

TIA

Keith