Just thought it might be worth pointing out that Ad-blue isn’t that expensive.
Less than £10 for 10 litres. My old C4 Grand Picasso used around 10 litres every 12,000 miles.
Even Aldi and Staples stock it.
Some cars are more of a pain than others to fill, the Citroen filler cap is under the third row of seats whereas Mercedes put the filler cap next to the fuel cap.
The only problem I had was the low-level warning popping up when I was on holiday in Germany. However Motability advised me that I could visit a local dealership, keep the receipt and claim a refund when I returned. In the end, it cost me less than €10 for 4.5 litres and I didn’t see the point in claiming back such a small amount.