Thanks BigJohn. Isolator looks ok – in that all the greys are going to N, blacks are going to L2 ad browns to L1.
I’ll get hold of one of those pens – sounds like one would be useful in the long term. Although the lines in the loft couldn’t be tested in this way unless I hold an earth cable up to me.
I tried swapping LS and L at the fan, didn’t make a difference. Swapped back. Fiddled with the timer and the fan has come back to life – although again permanently on instead of on/off with the light switch. Bah.
Pics here
At the fan (yes it’s isolated, yes I still wear gloves anyway, sometimes)
At the isolator switch
At the light switch