I got the bass back from Laurence Dixon (The Bass Place, Herne Hill) today.
He installed a Realist pickup (at my request, and in addition to the existing one), replaced the bridge with an adjustable (again at my request), shaved & profiled the fingerboard to match the new bridge, sorted out the twin soundposts so that they are correctly positioned and work properly, and did some corrective work on the end-pin structure.
His work was every bit as good as Clarky told me it would be, and the bass is instantly far more playable and more comfortable to play. It also sounds noticeably better.
I wanted the Realist since the existing pickup arrangement did a great job of picking up the sounds of the strings and of the slapping, but disguised (almost completely) the sound of the oil-drum. The Realist picks up far more of its sound from the resonating body and that means that you can actually hear the aluminium. All I need now is to run the two outputs through a blender and I will be able to control how much oil-drum the audience hears.
The adjustable bridge allows me to switch between a rockabilly setup and a blues/jazz setup at will.
The rest of the work was, frankly, remedial. As I mentioned before, Dave Gartland is not a professional DB luthier and he doesn't claim to be one. The bass as delivered had a few flaws which were easily fixed (well, "easily" by someone like Laurence), plus one which it is stuck with.
As far as I'm concerned, it is now fully giggable and I'm looking forward to doing exactly that.
I'm also expecting a fair bit of trepidation from any sound engineers who have to deal with it ...