Thanks again Ben ! I went to Bunnings & bought a packet of 10 off stainless steel ties, 4.6mm x 250mm long, for just $4.60. (Electrical Section)
Looked pretty much the same as the ones that came with the fibreglass wrap. Same design, same technique. Tried one when I got home, & it was like "chalk & cheese". These pull up nice & tight, & do not slip back at all. The packet was labelled by a company called STAHL, & were made in Taiwan. I'd say the ones that came with the kit were a China copy, where they didn't quite get it right.
Tie wire is a good idea. I might give that a try around the "collector" area. Actually, if you look closely at the area you highlighted above, I did leave one of the temporary plastic zip ties there to see how it fared with the heat. The big one going around the collector is a long one that was supplied with the tape kit, but it is loose, so I might pull both these off, & tie them off as you have suggested, & see how it looks & works.
Cheers Banjo