Thanks all for the responses and suggestions: Taking the marriage certificate along would be cool - although I'm somewhat wary of there being a computer says no situation at Heathrow leading to a great start to married life ;-) I guess to avoid this I'd need to get something in writing from BA and/or Qantas - but not sure where from?

Simplest two options as I see it are:

Get the ticket name changed - although having already done one lap of the feedback of no's from BA/Qantas yesterday i'm not sure what the next move would be? Calling BA and insisting? As I'm coming back in A could I chance my luck with Youfirst?

Alternatively just get the wife to be to renew passport in her maiden name although she is keen to get the Thelonius surname soonest - and to think I thought she married me for my looks ;-)