I'm in the same boat, got a luxury SUV (J6, Volvo XC90) for £390 (three-day weekend rate) which is a bargain and that car apparently doesn't exist in LHR (checked various days from now to December).
There's an intermediate Vauxhall Mokka SUV for £500 though.. I think £390 was a mistake rate.. will Hertz honor it?
I looked at the pictures, there's Porsche Macan, Bentley SUV, etc... and I'm PC.. hmm, the possibility of an upgrade.. LOL