Appreciating that they're not going to last forever but one was beginning to crumble and distort and clearly wasn't up to the job anymore.
I've spotted this alternative and can report it seems better made and, handily, needs 13mm spanner to tighten/loosen as required unlike the Discarnect that comes with 12mm nuts. Cheaper too.
In place on the GTL

Where I bought from - http://www.amazon.co.uk/gp/product/B007 ... TE_3p_dp_1 - I've since bought two more to replace two other Discarnects.
Sharing for interest.

