As usual, they sold me a tank of fuel which could be reimbursed if I returned the car full.
I drove around for the week until it was rasping empty and then filled up for €33 which came out on the statement at £29.
Also on the statement was the original bill for the fuel - £59. They indeed credited my account once I had returned the car, but still...
£30 markup on a £29 tank of gas! That’s over 100%!!!