www.ultimatehandyman.co.uk

Come on lads help solve this one.

Background

New build housse (2 years) - loop system used.
Outside light/ security light (those that switch on when movement is detected) blew a 40w bulb.
Bulb replaced but all other lights downstairs off. Easy, check distribution board for circuit breaker trip - NO trip.
Removed c/b and swopped with upstairs one. Upstairs lights still work. Downstairs with 'new' c/b NOT. So obviously not a faulty c/b.
Check all downstairs light bulbs all fine.

Any suggestions?

sound like its time to blow the dust from the electrical mutimeter, and do some live & neutral testing.

Something similar happened a while back-

viewtopic.php?t=1016

Read the post by sparkydude

Was has happened is that you have had a bad connections and when the circuit blew it disturbed the loose wire meaning tripping all the lights in the circuit out.

Open the consumer unit and check for loose connections to the mcb and neutral of the circuit in question. If none there then if possible, try and follow the cable to the 1st light on that circuit and check that ceiling rose again for loose connections.

More than likely one or the other as you have no lights working at all.