Final payment is 11,442
They have offered to finance it over 24 or 36 months at 8.9% both of these options put our payments up considerably.
As above, you might be able to get a better rate by going with a high street bank. Although the exact rate you are offered will depend on your credit history.
It will be higher per month, but it's a completely different type of loan. The interest you pay will be much lower and you have no large final payment. Whilst the monthly may be higher, the cost will be lower.
You can certainly ask RCI for a discount, but I'm not sure how successful that will be. I've heard of reductions when the final payment is much higher than the value, but I'm not sure that is the case here.
To reduce the cost of the personal loan, I would use any savings towards the car that you can spare and borrow less.