Thanks everyone for your responses. To all the people saying "wait" - you are absolutely right, that is definitely one of the options. However the spec of the car is quite rare so with no liquidity in the market, there's no guarantees that a similar one will be available in a month or so's time...
Apologies, just after some genuine help here and not trying to humblebrag or anything like that, but I just cannot work this one out..
So I want to buy a used car this Saturday for £53,995 (so the "as new" depreciation will have been taken off). I have paid a £1000 deposit, There is a remaining...