We got into rent arrears a few years ago, we had to claim benefits and housing benefit took ages to sort out, I was in touch with my landlord straight away and they were brilliant.
They told us not to take payday loans because the council will backdated and they know they'll get everything back, but in the rare case that they wouldn't, we can arrange to pay a little more rent each month until areas are cleared, rather than dig a deeper hole of debt via payday loans. Landlord was brilliant, they said that we were one of the few tenants they have that pay rent promptly and that they wanted to keep us.
There's times we live hand to mouth ourselves, it's stressful and worrying and we both felt that we needed to build a bit of a buffer so sudden changes like job loss, car fucking etc won't out us in a heat or eat situation. Ideally we would have liked a two month pot that would cover rent, food, bills etc. It meant that we couldn't have a wedding as such, and got married in registry office, used bus to get there (had no car at the time as was costing too much for the amount we used it) cheap rings from Argos, wore clothes we already had, no guests, cost less than £100 in total.
A couple of people were offended because they felt we could have invited a few family and paid for bigger room at registry office and just booked cheap resteraunt for food and sneered at us for choosing a "paupers wedding" rather than choose to celebrate with family and friends. It wouldn't have cost us that much apparently and we were selfish for only thinking of ourselves LOL, we didn't feel comfortable spending money on those extras as if dh work went bust we'd be fucked and would rather have money that would have been spent on resteraunt meals for 10, new clothes, posh rings put away for rent buffer.
Are you sure that your partner doesn't have any more financial ties with his ex?