Just an update.

I used the contact us facility on the website and I got a reply with an hour. It is an issue with the type of booking I was trying to make. I can book LHR-BNE-HVB but cannot book LHR-MEL-HVB..I have to include BNE.

I might now have to ask why I can book LHR-BNE-HVB and return.......but if my outward is via MEL as above there are NO return flights available HVB-BNE for my return despite them being available for the other routing..same dates. I guess these are still post QF glitches.

Whatever, I am impressed with the response.