"Chris Green" wrote in message
...
I want to fit a PIR to a corner of the house so that it will detect
people approaching along either of the adjacent walls. Strictly
that's 270 degrees but I've never seen a 270 degree PIR. :-)

I can't see anything that obviously fills the bill from Screwfix or
Toolstation.

Can anyone recommend something that will do the job

A pair of them.

and won't cost an arm and a leg?

A pair of the Hue external PIRs and the Hue system
is much more trivially programmable with time of day
and light level if you need that, but isnt cheap at all.
Amazon does very decent specials on those tho.