Hi --- In fact the sale is now concluded and the deal is done after such a period of time, the word of the salesman could not be relied upon unless he was to actually confirm that he said this.
When you enter a three way credit agreement upon which the sale depended, in this case ....your SIL, Carcraft and the Finance co.
You then only have a very small window of opportunity to cancel the finance deal and terminate the whole agreement. This can only be done by sending written confirmation of your desire to cancel to the finance co. before the authorised signatory (usually the manager) signs the agreement at the finance company end, once this has happened the deal is legally completed and cannot be undone.