First off, you don't want a car with cheap replacement parts : you want one where the parts last a long time. A cheap exhaust isn't cheap if it rusts out in 2-3 years, versus a more expensive high-quality one that lasts a decade.

Same for brakes, etc. My BMW the brakes are expensive, but the original pads still have loads of wear at 3.5 years old.

Really small engines can be horrible and gutless. Which means you have to work them really hard, negating any fuel savings. So you end up ragging the engine all the time to get anywhere AND using lots of fuel, where if you had a slightly larger engine you'd be driving it more comfortably and gently, meaning you end up using less fuel in the long term.

If you can stretch that a bit without burdening youself with debt then how about a new Dacia? Basic for sure but new car warranty.

I cannot stretch my budget over £4,000. £4,000 is my absolute maximum.

Thanks for all your replies