Well guys thanks for your help - I understand a lot clearer what is
going on now but still am unable to get the switch working.

To summarise here is how the fitting is wired.

On the fitting end there is a plastic connection block with obviously a
blue, green/yellow and brown cables connected as neutral, earth & live.

On the ceiling / circuit side I have 3 sleeves of cables - 2 of these
contain red, black & earth strands, the 3rd (the switch circuit) has 2
reds and an earth.

On the ceiling side of the connection block i have taken from the non
circuit cables - 2 reds into the live, 2 blacks into the neutral and 2
greens into earth. Earth also has the green cable from the switch
circuit.

So this just leaves the 2 red cables from switch circuit - I tried
Johns suggestion of putting one of these on each live side of the
connection block but again no joy.

Can anyone spot where i'm going wrong ? - maybe I need to try changing
which side of live the strands from the switch circuit go.

Sorry about this guys but i think we're very close to cracking it !!

Thanks again,
Mike.