A friend of mine, Kenny Lyon, has opened his own software development company, TableTop Software.
He’s primarily a .NET developer (though he has experience in a variety of environments). He does windows apps, web-apps (standards compliant, he’s a freak that way) and so forth. I’ve worked with Kenny on a number of projects and he’s incredibly good.
If you’re looking for a contract-based UK-based .NET developer, you could certainly do worse than TableTop (ie: Kenny) 