Fixed it! took the light that stayed on back to B&Q, replaced it and all is well.
Moral of the story? (two really)
1. Look for the most obvious solution first
2. Don't shop at B&Q
Thanks all
Hi, brought a PIR activated wall lantern for the front door form B&Q to replace the existing non-PIR lantern. Works a treat! so brought two more to replace two non-PIR wall lanterns at the rear of my house. Wired up ok. Turn on from switch as (as stated in the leaflet) they both turn on after 5...