Thanks all.
I know about the KlikFix bracket. I have one of those too and I agree, it’s much easier to fit and remove
I also know about the hole in the Ortlieb bracket to take the end of the wire. However, the fitting instructions DO say to cut the wire leaving 50mm exposed which is placed in the hole. A new wire measures 104cm and the instructions also say that any less than 74cm then it won’t work. So according to Ortlieb anyway, the wire is a single use item. (Unless the instructions have recently changed*).
A new wire is only £10 so not a big deal and I now have a replacement. I shall try to fit the bracket without cutting the wire and see if the entire surplus length will fit into the hole in the bracket.
* Edit - No, they haven't, I've just checked.