The carpet is not glued to the tunnel. It is held a bit by the hole at the top front where the black rubber hose for the battery box drain goes through the carpet. Then there are 4 snaps, two on each side down near the floor. Mine came that way in 1958 and I put new snaps in my new carpet tunnel in the same places when I was finishing my total body-off restoration in 1990. There is a cushion type of felt glued to my tunnel to absorb the sound and the heat. Originally it was tan coloured jute but I used the underlay felt in 1990 exactly as mine was when new.
The rubber plugs for my TR3A are under the carpet. Don't tell any TRA judges but both the plug for the gearbox dip-stick as well as for the front end of the driveshaft grease points had the black rubber plugs visible when I bought my early TR3A new in 1958. With them hidden under the carpet, things stay a lot cleaner.