Spot on. I put a newspaper over the top of the connected ouverture and the problem disappears.
It must be because I have the ouverture as option 2 and the BV32 as option 1. The thing is I find it irritating having to use AV to get the tv sound via the speakers and this set up generally works. (The speakers are connected to the ouverture, and option 0 on the TV doesn't get a video command so no picture appears, just sound - well that's my guess).
I'll just have to live with two controllers or get a surround sound module for the tv.
Thanks for your help.