Help with the impossible - cheap £4k diesel auto

[Nomisf]

Despite repeated, agonising attempts to force a comprimise - my 70~ year old parents in law are absolutley insistent that they want the following seemingly impossible car:

• Auto, Diesel
• Hatchback, Small MPV (No Estates or Saloons)
• >35mpg
• <= £4k to purchase

Every week they send me a new AutoTrader link to something suspiciously cheap with an unreliable early robotised autobox (was a 2012 Picasso EGS last time) and want me to give it my blessing. They got conned by a dodgy dealer on their last car (a crashed Civic with dash warning bulbs drilled out and reisistors for airbags) because they didn't listen to me - so for my sins they are now beholden to my advice.

So my question is - what is the least-worst option in this field? I know they are all bad - but what won't just be a disguised autobox fault waiting to greanade. If it were me I would buy a slush-o-matic Lexus - but they won't have it.

Help

 

[Nomisf]

Something like this - https://www.autotrader.co.uk/car-details/202404048277594?sort=relevance&advertising-location=at_cars&fuel-type=Diesel&make=&postcode=se9 6hz&price-to=4000&year-to=2024&fromsra

I have tried so many times to get them to consider a manual as it would make this a lot easier - but mother-in-law has decided she can only drive an automatic and it would be easier to walk to the moon than persuade her otherwise.

At 4k nowadays it's going to be a complete roll of the dice, 4k is the new £500 banger unfortunately

At the bottom of the market i'd want a proper old torque converter slush box as anything else will be either terrible to drive, a ticking time bomb or probably both such as a robotised manual or a CVT

That's pretty much the conclusion I have come to - but I am still holding out hope that someone can think of an overlooked unicorn car !

 

[Nomisf]

Why do they insist on a diesel.
MIL has a Venga 1.6 petrol, every time I get in the long term average economy is >40mpg.

Older ones in your price range.

The usual list of justifications that used to be true but aren't any more - not helped by their last "new" car being a PD 1.9 Golf that went to moon mileage. I am putting together a list of Petrols to see if I can tempt them so will check it out!