Thanks for the interest in the follow-on B7, and regarding fittings I'm reasonably sure they should be capable of being offered separately from the boiler. Some of them, as pictures have shown, are produced in a multi-part mould and would have to be supplied as a set.
As my fellow conspirator is burning the midnight oil trying to get his chunk of the "full prototype" ready for an auspicious union with the resin parts later this week, and has therefore only found time to post his latest update over on the "no criticism of large manufacturers or of dumbed-down television programmes permitted" website, I hope he won't mind the fact that I've stolen his images and that I am about to post them here, in reduced form. He can take issue with me in person, mid-week, if necessary....
Later today I also hope to post images to show that partly in response to comments I have striven to produce alternative castings for tall (as per early photos), medium (as per official drawing) and later low versions of the dome cover, along with a plant-pot chimney that is as close as I can get to the type shown in photographs, given the limited time that is available.
Just to prove that the principle of smallest things causing most trouble is alive and well, I'm also on at least my fourth attempt to make an effective and durable mould for extra sandbox lids.
I must go now. Time and tide wait for no man.