Quick update - lifted the front footwell carpets. Right hand side (drivers side in Scotland) is soaking wet. The foam backing of the carpet holds a lot of water!
Left hand side is dry.

I cleared the front sunroof drains with some plastic tubing, quite a lot of leaves/ debris removed, so I'm hoping this was the issue

Any suggestions as to other likely place (s) for water ingress would be greatly appreciated!

eta Is there a diagram/info on drain holes for the T model 124's available anywhere?