Will double-check them, but they looked ok on a first inspection and,
pessimist that I am, as both front footwells are equally damp, I'm assuming
that points to the matrix? Or would a leaking joint at the pipe dribble into
both footwells? However, as I'm not getting condensation on the screen, so
the optimist in me says maybe it is just a weeping joint? Fingers crossed,
as my enthusiasm for pulling the matrix out is not great! I'll have another
look at the connections in daylight and, if I can't find anything wrong,
bung a tin of Radweld in and see what happens!
Simon

I've used Radweld three times and twice it has worked a treat.  Once was
"on the road" in an old Citroen that was dripping water fairly quickly
out of the bottom of the rad - enough to cause a stream of water within
a few minutes of stopping.  The guy in Halfords where I stopped was
very helpful and fetched me a couple of kettles full of water - he was
amazed himself that it stopped such a leak.  As someone else said, I'd
check the pipes first, but if it is not that then I'd definitely
give Radweld a shot.  It won't do any harm to the RR.

Matt