Much as I hate waking long dead threads, I felt I had to confirm this works for the Freidland Battery operated PIR. F1023R Wireless PIR Movement Detector - Product ref 40054676-001 , which was sold in a B&Q in the UK up until a couple of years back.
I have a couple of these PIRs in my junk box, and dug them out for a bit of fun. A quick Google trawl on the partially obscured controller chip on the board told me they were Holtek based, and a little more digging brought me here.
I get a fairly usable result in the serial monitor from the above code every time the device is triggered...
1048575 15
1048575 15
.. not 100% reliable, I do see quite a lot of noise... but all in all not bad for starters.
If I get some spare time, I may look at enhancing the code...