Thanks everyone. I think from my point of view there's two reasons for the hallway PIR. There is the small cloakroom with entry from the hallway which has a window - so the PIR covers anyone getting access that way as well as the entry door. The other one is the reminder the alarm is on. Saved me many times when we have guest staying overnight: Even though you tell them the alarm is on, I can't remember the number of times they head down at 6am. The hallway PIR has acted as a wake up alarm so I can run down and turn it off .

I had one other question - what's your opinion on PIRs in the bedroom. The downstairs is extended at the back with a pitched roof. This sort of gives easy access to the back bedrooms upstairs. Would you recomend PIRs in those two bedrooms?

If the rooms are occupied at night then a suggestion would be shock sensors on the windows 

17 hours ago, aissecur said:

If the rooms are occupied at night then a suggestion would be shock sensors on the windows 

Thanks, that's a good point.

Part sets?

21 hours ago, sixwheeledbeast said:

Part sets?

Thanks. I acutally did wonder about that and having read up on it, that may be the better solution: It's easier to wire up a PIR than the shock sensors unless I go with a wireless expander.