400k for 7 months = 37k per month, then you need to put back 400k over 5 months = 80k per month. I would rather do my way, Combo, of 400k in the bank and 35k per month. No thought needed.
OK, the 400k (GBP10,000) you are going to pay back could be in a bank account @ 5%?, which is 0.41% for each of the 5 months = GBP 208.33 which you could not get.