the feds are onto you as we speak, and I doubt you'll come out of prison this side of the next millennium.
Technically you have indeed committed an offence, but you are unlikely to hear a knock on the door. I move around London most days, and I pick up hundreds of insecure networks - at the moment I'm in a client's office in Notting Hill and I can see seven unsecured networks within range on my laptop. It's a problem that is growing - people don't realise how easy it is for someone else to steal some of their bandwidth, and with wireless routers growing ever more powerful I expect to see the situation get a lot worse before it gets better.
As far as you are concerned......you've been very naughty, and I don't want to hear of any repetition.