So your commercial options for mounting boards are fairly slim and generally kinda garbage, from what I've found. I don't know much about what's available in the UK, but her we have MBA and Lockmasters which offer a practice stand that's made of plastic and fairly thin... they'll do the job, but they're a bit flexible and not very pretty, and because they're so thin you'll have to cut your dial spindle pretty short and will need to replace the dial if you decide later to remount on something thicker.
Most of us make our own mounting boards. Really, any good flat board will do, I prefer something around 3/4" (~19 mm) thick. If you buy the lock new it will come with a sheet detailing the mounting holes layout, which you can use to measure. It can be as easy as drilling a hole for the spindle and just using wood screws to secure the lock to the back and the dial to the front, but you'll need to adjust the spacing to get the feel just right... my first board was just a scrap piece I had laying around, and I just used paper as shims, but thin washers work well, too. You can, of course, get as fancy as you like if you're handy... Oldfast has some really nice mounts pictured in his 'Chronicles' posts, and I recently mounted my collection on some red oak boards with brass threaded inserts on the back and laser-engraved model numbers with a nice oil finish:
The threaded inserts are kind of a pain in oak (drill bigger than they recommend, take my word for it), but they're nice because you can leave them proud and adjust them perfectly flat and to just the right thickness for a smooth action by turning them in/out slightly, and they'll allow you to use the proper mounting screws. I'm totally obsessed, so I used an indicator on a flat piece of granite, turned them until they were close and then flattened them further on 800 grit emery paper to get them perfect. Not entirely necessary, I suppose, but they turn like butter