Thanks, got the box in the loft now, with the help of 20m USB extension which works well. Antenna feed now < 1m.
All 'hardwired' to my home office PC, then I use my wireless laptop to roam around the house/garden to RDP to the main PC and run the application.
My loft has a couple of fluorescent lights, and I have noticed without fail that turning these on causes the connection to the hardware from the PC to drop, with only the green light remaining on. Disconnecting/reconnecting the USB gets it talking again.
Perhaps this particular issue is for discussion in another thread.