Thank you all for your input – very helpful, and I’m pleased to say that having now gone further down the rabbit hole, a Beo4 remote has solved the BL3500 issues and is now working perfectly with the BS3000! Success!
the BL4000 is another story though – I had thought they were connected to the BL3500 (is that even possible?!) as a link, but having failed to get them running I assume the issue is not having an IR Eye? Do I need one for the BL4000 assuming they are set up as a link? And does the IR Eye connect direct to the speakers themselves?
thanks again!