Caveat that I'm not familiar with the UK car market.
In the US, popular Honda and Toyota models, which are widely believed to be far and away the most reliable and best fuel economy (although I think others are closing in) have interesting used prices. New will have amazing financing at times (0% or close to it) and you can negotiate off the list price of course. 2 years old will often be priced the same as new, but with no incentives like 0% financing. You have to get 5+ years old to see much of a price drop.
We have a Civic that was bought new in '02 (and '03 model) and we are still driving it. Its 14 years old, ~145k miles, and really has not had problems. A few minor things like auto windows going out, but nothing major and $$$. Maybe it was stupid to pay so much for the new car upfront, but looking at the life of the car, which still has probably 5 to 10 years of life left and has NEVER left of stranded or been unreliable in ANY way, I don't think it was a bad decision.
That said, when we replace our other car at some point soon-ish (its transmission is going) we will likely aim for 5+ years old with around 100K miles, as we just don't want to spend the cash on the upfront cost of a new car. But OTOH, after an hour or 2 in slimeball used car dealerships, I may say F it, and run screaming back home to negotiate a new car deal all over the internet, lol. Maybe that is different in the UK but lets just say that every used car buying experience I have had in the US other than buying from family has been.... very negative.
That was rambly and all over the place. Maybe some of it was helpful?