I seem to have bought a new Erdé two bike trailer from eBay: now all I need to do is get the towbar fitted to Mrs. Blue’s Fester (as I can’t get one fitted to the ST200 ).

Should make travelling to and from circuits easier, plus I can carry spares and tools.

[edit]
I spoke to the sellers and they let me upgrade it to the bigger, 750kg trailer which arrived this morning.