How much rain do you manage to get?

I don't know how much we get exactly in our water butt, but it seems to work out the right amount. I don't ever have any overspill, and I'm never stuck for having enough to water the plants with either. So I do think that I have the best of both worlds. It would be interesting though if any of you know how much water you actually manage to collect, as it would be good to hear! Also would be great to compare how different parts of the country vary, and whether your collection method can make a difference at all.