It will not work out financially for you
You are well above the £1k mark already and you have to budget for brakes, exhaust, clutch, coolant and gear oil, any rust, battery, tyres, suspension bits, filters, etc
It would made sense if you were buying a younger model but an almost 10 years old car is a risk
You can buy these cars around £500 at the auctions, about half the money of any works
Then you can do these 500 miles per week, scrap it and buy another
Brand new small cars are now around £6k and so for 25k miles per year, you will spend more money upfront but on the longer term, you will have peace of mind
Test drive one of each before you part any money and ask questions about the maintenance
Keep in mind that the timing chain can turn out to be a service item every 20-30k miles, each time costing £1k, and any works at the injectors, is not just the seals, you will need to replace the fuel lines as well