It is not a good idea to start a 12 month policy then cancel after 3 months. There will be a penalty charge for cancelling so you will probably have to pay something like half a year's premium for quarter of a year's policy. Paying in installments wont change this but it will just make it easier to dodge paying. When comparing quotes, you should look either for a company willing to issue a cover note for just 3 months or for a company that wont penalise you excessively if you cancel the policy after 3 months.
Remember that if you are overseas for more than 2 years, it will be difficult (without a lot of shopping around) to continue with your previous no claims bonus. When I went abroad for just over 2 years, I let my old policy continue for the full 12 months (with no car and no me in the UK). The policy was worthless for anything other than letting me come back to the UK within 2 years of it ending and claiming some no claims bonus.