Interesting, a quick phone call with The Keyboard Company based in Gloucester has given me the answer, and I hope it helps fellow Mac users who wish to employ a FILCO NUMPAD. It is the EQUAL KEY that causes the unit to effective crash and renders it useless until 'rebooted', but un and re plugging the USB cable.
ALL other keys work as they should bar the 00 key and the EQUAL key, pressing the latter does not work and it does not 'de-press' according to the computer, hence the freeze.
I did not realise the profile of the numpad is rather unique, but for the time being have placed a RED FILCO KEY CAP where the EQUAL key goes, as a subtle reminder, not to press. Otherwise of the sake of £16.50 and free delivery, I am delighted. I gave the whole thing a jolly good clean but testament to FILCO's robust build quality, it shined up, almost as key. The keycaps are a different story, but I use a tiny about of 'Bar Keeper's Friend' - cleaner and polish on them, and the whole unit body in fact, hence it's almost as new looks now. This polish looks to have given all the keys an almost factory like finish, it has a very gentle cutting compound and I've been using it for so many things around the house - from my Dualit toaster to my newly acquired secondhand KBs! Always test a small patch first and only use the smallest amount.
In conclusion, I think this unit, the FILCO NUMPAD is terribly overpriced at nearly £50, but I did bag a bargain after all. Also have contacted the developer of KARABINER to see if he can work his magic for me and re-pgraomme the EQUAL key to avoid this crash - perhaps impossible but worth trying.
