Thank you one and all for your replies and assistance!!!
Stan2004: I didn't see any "magic smoke" coming from the TVS when I tried it a couple of times on the track, before I gave up and finally removed it from the wire nuts. When I did this, everything went back to normal.
And yes, the sales assistant at the electronic store did say that the "banded" end must be fitted to the centre rail hot wire, that's why the TVS's were sold in strips with red tape and white tape at each end. The red tape indicates this is the end to go onto the + (hot) wire, and the white tape end goes to the - (ground) wire.
Guess where I am off to this morning (Monday down-under here) with a strip of TVS's in my hand!!
Just a final comment......Stan2004 and Gunrunner John's comments made me smile (laugh out loud actually), and added a bit of levity to something that absolutely frightens me to death - modern electronics. Thank you both!!!
Peter (Buco Australia)