The residency legislation can be found here http://www.legislation.gov.uk/uksi/2006/1003/contents/made

and the related driving licence legislation is here: http://www.legislation.gov.uk/uksi/1999/2864/regulation/80/made

But keep in mind that residency and citizenship are two different things and that residency for tax purposes can be different from normal residency however you are normally considered as being resident if you have spent 183 or more out of 365 days in the UK. My understanding is that you would then need to leave for at least two years to no longer be considered resident. DVLA says that although you can only drive for 1 year you have up to 5 years after becoming resident to exchange a licence.

So I think that, yes, you are resident and you became resident when you arrived in the UK in April but it's only my guess. My sister recently swapped her foreign licence for a UK licence and she said it was easy and quick.

The answer is very simple - don't stay 12 months in the UK - even a short trip of more than 24hrs to France or Rep of Ireland or any other country is enough. Then a new 12 months starts. Going 'home' is not the point - it's going out of the UK that matters.

By my reckoning you've not been in the UK for more than a few months.

My wife is also dual Nationality - we were married 20 years ago - and neither of us has spent 12 consequtive months in the UK.

All this exchange licence stuff is designed for people who are / have become permanently resident. We spend some months in the UK and some months outside the UK and even outside the EU.

If you are married to a British Citizen, you must have been living legally in the UK for 3 years continously and must have been physically present in the UK on the date three years before you apply for Naturalisation. You must not have been absent for more than 270 days in total and not more than 90 days in the year immediately before you apply. You must show that you are settled at the time you apply.