Hi Joseph
Thanks for the reply.

Would voltage drop affect only the last four fixtures on the line and
each of them in exactly the same way?

I will check all the connections again on the weekend, these were not
the piercing kind, so it could well be my fault for doing a bad job
when connecting.

I will concider all your options and see how it works out.

Oh, I also wondered if LED bulbs would maybe solve my problem? I have
read on some sites that they are much more tolerant in conditions were
voltage drop exists.