Spotless water is good...if it's working properly.
I only say that because they have just closed one location in Bournemouth.
Just turn up and follow the onscreen instructions. You won't have a 'fob' so don't worry about it.
It will cost 3p per litre plus VAT and you can use your debit card to pay. Don't put your debit card in the reader, (use the contactless on the right hand side) much quicker.
If you put your email address in, when prompted, it will send you a receipt the same day.
Think of it as a modern petrol pump at Sainsburys and you won't go wrong.
Make sure it has access 24 hours a day, or you'll need a code for the gate lock.