Following a leaking stopcock, badly damaged damp wall and subsequent fixing…. I am now about to box in the stop cock again!

the main comes up through the floor, next to a wall and runs along the bottom of that wall for about 3′ before heading upwards.
This was boxed in using a bit of skirting board and a 3″ piece of wood bridging the gap from the SB to the wall.
This arrangement does not allow any ventilation, leading to excess condensation on the pipe.

What can i replace the wooden top with to allow airflow, even part of the length may suffice?

Just insulate the pipe?

Yep,insulate the pipe with foam lagging and seal the joints with tape.

what about the stopcock itself?