i noticed when i payed my greenlight insurance last year, in instalments,
it was a credit agreement made with a loans company, and not a DD to greenlight themselves, as would be the case with larger insurers.
you will still have to pay the full amount i'm afraid.
i would only take out a greenlight policy if i pay the full amount up front as i did this year, and now i cancelled it i even get some money back....not much though