Car appreciation... the aesthetics, the engineering, etc

I would only consider it because I've got enough experience and tools to keep one on the road. Most people are not going to know what to check when the alternator light comes on.

Old cars also smell funny.

This would be me for sure. I avoid London like the plague though.
Also people can't be trusted to maintain and look after them now.

No 40 year old car is going to be reliable, regardless of how well it's been maintained, unless it's been reconditioned, in which case it's going to be expensive.

There's currently 809 ULEZ compliant petrol cars available on Auto Trader for £2k or under.

£2k's worth of 40 year old car will not get you fun and smiles, it will get you starting problems, overheating, rust issues, obscure parts not easily available and an intimate relationship with your local recovery and roadside repair drivers.

On top of that, let's add the safety implications of driving around in a 40 year old car with a non-existant NCAP rating.

On top of that, if everyone who currently owned a non-ULEZ compliant car, bought a 40+ year old car instead of buying a ULEZ compliant car, we'd end up in a horrifically worse emissions situation than we're currently in.

It's a nice idea, and I have considered a cool 60s or 70s muscle car just to cruise around town, but I know it's not a sensible idea and I can't afford the cost of ownership let alone the cost of buying a half-decent one.

On top of all that, as mentioned by other people, I once had to pull over on a motorway slip road with no hard shoulder with my baby in the back and that was a stressful experience I do not want to do again. It's OK breaking down in town where you can just stop on the side of a road or even coast into a side road, but having to use a 40+ year old car to do regular 100+ mile trips with a family is not the type of anxiety I need in my life.