Not sure what to do about leaking roof

[saltire]

The flat roof on the house we own but rent out is leaking. We have had a quote from a local roofer for just over £900. It needs done now, and he has said he can do it this week. However, our money to pay for it won't be through for at least another 4-5 weeks.
We have surrendered our endowment and using a lump sum of it to reduce mortgage. The remainder was going to be used for a holiday but now we need it for the roof.
Do I explain this to the roofer and have him wait until it comes through before he does the work. It is leaking into the bathroom and it has been (and probably will be now until April) non-stop rain, so it's only going to get worse.
Or should I explain it to him, ask him if he could put some sort of cover/temp repair on it just now?

Is there any way you can find out how fast your roofer is in getting his bills out? The friendly local builder who redid our kitchen in April didn't get his bill to us until July, despite us chasing him for it several times (too tempting having more money than we ought to in the account)!

Or explain the situation to him and see if he is willing to wait for payment, or if you could arrange to pay in instalments, or if the damage and costs will increase if you defer the work for a few weeks.

Usual business terms for payment (if he's VAT registered) is 30 working days - some let you stretch to 60. I'd have a word with him