Howzit, MrB? Those charcoal holders look good, but pretty expensive?
Mine's only an 18.5 in model, but I just leave the indirect wire things in place and put the lumpwood charcoal either in the centre for direct cooking or outside for indirect. They work just fine!
Weber have stopped making the excellent ash catching device on 18.5s - heaven knows why. Only that useless hub cap thing and 3 finger biting wore clips now.
Fired it up yesterday evening - as quick and easy as ever!