Yes - 4 twin and earth into the junction box - but in two pairs .
Yes the lights have all worked - for atleast 5 years.
No work done in kitchen or anywhere else.
Ref faulty light - see below for it still tripping with lights
disconnected.

I have tried disconnecting all the under cupboard lights - the
electrician actually put in three drops from ceiling - which terminate
in junction boxes fixed to underside of wall units. The inidivual light
fittings (3) are connected to a separate junction box at the bottom of
each of the three cable drops.

The lights (link lights) are connected to the junction boxes - so I
have disconnected each light fitting in case one of these has gone bad
....but this didn't make a difference. The only thing I can think is
that one of the junction boxes under the wall cupboard has corroded
inside due to moisture ingress and when the switched live is applied
this trips the circuit ??

Additionally today I tried bypassing the two "extension" cables (both
twin and earth) that drop from this junction box to the wall switches.
For the main ceiling lights the twin and earth is suppling a live
(preumably looped in from a junction box under the upstairs floor) and
the black wire is as expected a switched live feed back to the light
(it's not marked with red tape though). A simple test joining the black
and red from cable one (which is all the switch one would do) and as
expected the ceiling lights are on (once power back on of course).

Based on the use of the jumper from switch 1 COM to switch 2 COM I
believe the second twin and earth is actually only supplying a switched
live back up to the junction box supplying the under cupboard lights.
If I join the red (this must have been acting as switched live before
as black wire is taped up unconnected in switch) from cable 2 to the
live red from cable one I would expect the under cupboard lights to be
on.....but this trips the earth leakage cicuit breaker the second the
power is restored.

I also tried going back to standard fuse on the circuit instead of the
MCB - no differnce apart from I'm now a gew 5A fuses down.


Apart from the moisture what about mice eating throug a cable - I had
a brief look under floor upstairs today but no signs of any damage.

Thanks so far...
Nick