The big Italian tasting's at the end of June, called DIT, and usually held at Lord's.

I think there are some smaller ones before this, though. I've heard good things about the Gambero Rossi Roadshow which is in London soon.

In the meantime, it'd maybe be best to contact some of the agents with good Italian lists, Enotria for example, to find out what tastings they're involved with, or are arranging. Liberty also has a good selection of Italian wines.

where abouts in North London? I may be local to you if you would like any help.