Does it get wet only when driven? or does the car stay outside in all weather and no water gets in?
there are a few places to check, starting with door / window seals, including the scrapers on the door windows... My suggestion would be to wait until its all dried out, and then get someone to spray the car with a hose whilst you sit inside and try to see / feel around until you find the leak.
Another place to check is the end of the heater channel where it meets the rear inner arch. I had one rust through there and in heavy rain the rear wheels sprayed water up and into the heater channels, where it then ran down the channels and out into the footwells.
I'd start with the hosepipe, and see where that takes you, otherwise chalk is quite useful, rub it all along the edge of the carpet and see where it gets wet...
As for club meets... First wednesday of the month at the Aneurin Bevan pub by the A470 / A48 junction. Though club meets can be a bit sporadic, best bet is to head on over to the facebook group if you are on there, more chance of that being updated than here. I will be pestering Dude to send out messages about a meet this coming wednesday shortly, so hopefully we will have a few people there this month...
https://www.facebook.com/group.php?gid=2365548566