Just FYI, unless someone wants to sell you a pin wrench they had made (or got from Crewe) because they no longer use it, it will probably be much less expensive to have one made. There are several threads on this forum where those of us who have done just that have posted photos of the variations on the theme that we've had custom made for us, and for very little money. See: My custom accumulator pin wrench and holding jig for rebuilding SY accumulators.
There's not really much that's special about the accumulator control valves (ACV) as far as tooling goes. It's not difficult to get either a piece of bar-stock cut or an actual hex (male) socket to remove the end retaining cap on the ACV.
I have not, as yet, ever replaced the fluon pieces in the ACV as they've never needed it. See the image I included in this post, as it's very instructive about what's inside the ACV.
Kelly Opfar at www.britishtoolworks.com makes them. There is a small taper tool needed to replace the O ring and Fluon ring on the accumulator valve piston that you need. It is false economy to not replace these when rebuilding an accumulator valve.
I built my own rig so I can test and shim the operating pressures on all the accumulator valves I rebuild. Pretty well every one needs at least one shim to bring the relief pressure back up to factory specs.