Re: "between 2007 and December 2014"
How many major projects take multiple years, and how many take several years longer than originally planned?
"Terribly sorry, but we can't accept this contract extension because HMRC might decide that it makes me an employee.
You'll have to hire another contractor to finish this project. Yes, I know that will delay it by another year or two while they get up to speed, but by then you can hire my company again."