The number for the BSP valves is the one quoted at the start of this thread.
My valves, let's call them taps, are the other way up from John's. I used a male x male crossover on the female, lower tap connection, and one end of the crossover accommodated a nipple. This meant that if I screwed the male end of the tap (mine was BSPT), sans flange, into the tank, I'd 1) be able to use my standard Vin fuel lines without modification, and 2) I'd need to seal the thread. Sheer serendipity: ball valve plus crossover is almost exactly the same length as a standard fuel tap. I used Loctite Thread Sealant, and it has worked perfectly over 4 or 5 years. AND I can take the taps out without wrecking the tank. (I haven't had to use heat, took 'em out cold, but it doesn't take much heat to soften Loctite anyway, boiling water will do it.
In a thread on the same topic, someone told me that he had managed to buy mini ball-valves which were male BSP (not BSPT) and flanged both ends. Maybe they are still out there.
Why metric? My guess would be that there are enough old cookers out there built with REAL threads, to provide a demand.
Tom