Mmmmph, well I'm certainly lowering the average, working out at 10.5 mph, there or thereabouts LOL. Mind, a short plump lady on a 650c-shod bike isn't going to be the fastest combo anyways.
Out here north of Cambridge the roads are pretty flat for the most part. It's t'other side of Cambridge that's got all the hilly bits. On the other hand, when the wind blows out here there's nothing to stop it, and you can be pedalling for all you're worth and still end up going backwards...