They assumed you were paying them for doing your driveway. Always tip more.
Good shout - 20p wasn't enough. Althuogh they were excellent at telling my fortune when they said they were going to give me a good hiding.
I did eventually have a shitload of truoble after having my driveway done by a company called Millenium. I said htey'd done a shit job and the main man come to my house and demanded the payment in cash. i told him to fuck off and he asked if I'd like to say fuck off to the 15 lads on the minibus parked opposite who would have no money for the weekend and that they were thirsty. I told him that he could tell them to fuck off, shut the door and crapped my pants for an hour or so.