Twickenham Cyclist and Beebo are both pretty much spot on. The offence of going equipped is very much in use, and also very well known - I don't think you'll find many officers that haven't arrested someone for it.
However, despite what the poster says about bike thieves could be wearing full Lycra, they tend not to, their most common uniform of choice to be tracksuit, baseball cap with an option of a hoody if cold. Yes yes, I know I shouldn't stereo type but there you go.
Beebo's right about having trouble making it stick as well. If they have a lot of previous, it's not too hard, but a normal member of public, with no convictions, able to easily explain why they are carrying said croppers is really not likely to find themselves in any trouble.
Would I have stopped you... I've been wondering this since reading your post, and do you know, I'm just not sure. It's one of those where on paper, perhaps I should - however I think in reality, you, your outfit, your bike itself and (potentially) the manner of your riding would have possibly added up to meaning those police mans instincts wouldn't have been fired, and I too, may have driven right past you!