You could probably scrape a VW Arteon PHEV for £35k. Beyond that, it really comes down to your definition of 'Premium'. Brands like DS (DS7 / DS9) and Peugeot (508) say they're posh, but I think the interiors are nasty and they're French so come with that unspoken threat of breaking down. A Cupra Formentor might work for you but has no real brand cachet attached to it. A Kia Stinger would possibly be ideal, but says Kia on the front.

Obviously, the usual brands - BMW, Merc, Audi and Lexus all produce very capable and comfortable cars, but efficient, entertaining, spacious and relatively cheap / reliable are hard to come by these days.

I live in greater London and the impending ULEZ extension forces a reluctant sale of my much loved Euro5 640d. Everything about this car has been superb for the last 5 years but now is the time to move on. Requirements for a similarly comfortable, fast and entertaining premium car (ideally a coupe) that can accommodate 4. I do only 4k miles per year with infrequent long distance driving with a max budget of £35k.

I've discounted the 997 as examples within my budget are likely to require high maintenance and luggage space on longer trips is unusable.

I'm considering an M4 (2019 MY competition spec) but I'm concerned that future environmental taxes will price me off the road within 2-3 years. I don't like Teslas and whilst the Honda E appeals, it's no good for longer drives and is a long way off the 6 series for luxury. Any interesting alternatives I should consider?

Given your very low (normal - I presume that's pre-Pandemic) mileage, would you be able to get by without a car except for the odd trip out and the annual holiday? If so, why not - even as a short-term measure, sell the Beemer, use public transport/walk/cycle for local trips and hire a flashy sports saloon for those away days/holidays? At the very least they could be unofficial long term test drives if you're not willing to ditch having a car generally for everyday usage?

Given today's strike woes and as someone who's used London's public transport a lot over the years, I realise this may not suit you, especially if you live in South London and/or outside the North/South Circular (and thus mainly have to rely on buses or far less frequent/nearby trains/tubes), but it might be worth a try, even before selling the BMW.

The alternative might be to buy a smaller, nippy Fiesta-sized car (not a 'cty' car that would not fit 2 in the back other than small children, e.g. a FIAT 500) that would be good enough for the local work and perhaps some shorter 'days out', and hiring the larger sports saloon for the longer trips and holidays.

It would probably save you a LOT of money, including VED and insurance, and go towards other nice things. Bear in mind you've stated that you're concerned about environmental taxes 'pricing you off the road' whilst saying you can afford to buy outright a £35k car.