It really depends on how each insurance company defines 'resident', as they all have their own definitions. So, it'll just be a case of looking at the different company policies and seeing which ones you can apply for.
However, if you will be travelling for 6 months, you may need to try for a company that specialises in long-term travel insurance, as a lot of policies limit you to trips of no longer than 42 days out of the UK in one go.
I've just checked 3 different sites and they all seem to imply that you will be eligible for insurance with them on a spousal visa.
The STA Travel policy terms state:
"You must have been legally resident in the UK for 3 months or be on a UK student study visa in order to purchase travel insurance from STA Travel. You must also be starting your trip from the UK."
The Boots Travel Insurance policy terms state:
"You and all other persons insured on this policy must have your main home in the UK and have a UK National Insurance number and be registered with a medical practitioner in the UK at the time you buy or renew this policy. Channel Island residents must have their main home in the Channel Islands and be registered with a local medical practitioner."
The Endsleigh travel insurance policy terms state:
"These policies can only cover permanent residents of the UK who are registered with a GP in the UK. To be considered permanently resident, you must have your main home in the UK and if in employment are registered for UK income tax."
