Well, I thought I'd make my report: on getting home I tried both the IR and Bluetooth methods and neither works. Oh well I'll have to hang on to my old one.
I'm well aware that the BT list doesn't cover some of the more obscure makes (and that includes Toshiba who, it seems, buy in branded TV's from the cheapest vendor) but I would have expected it to work with a major brand like LG.
It might be worth reporting it as faulty and requesting a replacement
I don't think it's an issue with not supporting LG, more that the Pro Box can't see it because there's a Marantz amp in the way. Looks like the box has no support for amps.
Up to the OP whether he wants to connect the box directly to the TV to test.