All good advice guys, thanks.

I had another look today and resealed the cracked compound. I also got my hand up on the left side and felt a tiny rust hole that may be in the plenum, or where the guard attaches. I put some sealing compound in there and will check tomorrow with water.

The drivers side may be the windscreen. I'll pull the trim and have a look. These are only tiny leaks and it was really heavy rain, but I still want to fix them for peace of mind.