You paid for a "connection" service, not an "installation"!
I hate to say it but it's what these profit centric organisations do... Sell "easy peasy, one-stop" services, that are shrouded in terms & conditions, and leave dissatisfied customers in their wake... But it was only £15 so...
There were no terms and conditions, I just paid for "Connection". That means connecting the water and electricity, which they have to do to a proper standard.