Here's a link to Prudie's suggestion but they have a new one out on Thursdays so don't be surprised if there are some changes tomorrow.
https://www.autotrader.co.uk
Which car valuation site was it merton?
It'll be a natural discrepancy between looking at a forecourt price where they expect to be haggled down, so start a bit higher to accommodate for that and getting your value from a site like 'webuyanycar' where they value everything too low because they want to make money. Get your real value by going on Ebay and searching for the car you've seen, on the same year with similar mileage and spec, then go to completed listings and see which ones are in green that have actually sold. That's pretty much your true value.
Looking on Auto-trader, £1299 could buy you something like a 57 plate Ford Mondeo.
Such a purchase could be a real bargain, giving you maybe 5 years of motoring at a depreciation rate of less than £300 per year.
My advice would be to insist on a new MOT so that you don’t have to worry about that for 12 months.
With the greatest respect Merton, useful though Hymie's answer was (and it was), that was not the question you asked. Several of us answered your question, we were not being unhelpful, we were actually trying to help and trying to answer the question you actually asked.