John Rowland ) gurgled happily,
sounding much like they were saying :

I saw a rented smart car in London marked "£5 per day including 75
miles of travel".

Which means they charge you for mileage over 75 miles per day, on top of
the rental price.

Since this is less than I typically spend on petrol for my car in a day

.... and you'll need to return it full of juice, as with any other rental.

and I would presumably be able to go in the Kengestion Charging area.

Indeed. Under exactly the same terms as in your car - by paying the £8 or
the penalty charge if you forget (plus the hire company premium for
"handling" the fine payment for you)

But I can't remember the company name. Any clues?

Think I've seen 'em signwritten for Sixt.