Upvote:4
My American wife and I have joined the UK/EU queue may times and had confirmation from several IOs that it is ok to do so. The problem is that many UK airports employ private security staff to direct people to the right queue. It is usually with these staff that we have had to have an argument!
Upvote:7
You will have to fill out a landing card each and every time unless you are a registered traveller. It's the law and there is no way to circumvent this requirement.
Your other question is more interesting... You are directed to the 'other passports' queue because you do not have a British (or EU) passport and you want to join the accelerated queue for British passport holders. There is no set policy on this, but there is an overarching policy that immigration procedures should avoid separating families -- it's something they are reluctant to do.
So under that policy you can join your wife in the British passport queue and clear controls such that your family is not required to be separated.
There are exceptions to the policy...
As a general rule, you should proceed to the British queue as a single family unit (as long as there's a Brit in the party)
For your implicit question: there are no special breaks or carve-outs for Aussies, or any other Commonwealth national...