The law has changed since the company (Wiki Educational Resources Ltd) was formed two years ago. It is now possible to incorporate as a company limited by guarantee and charity on the same day.

I'm not sure that's true, but either way it doesn't apply to us - you need to have an annual income of over £5000 to register as a charity (as opposed to registering for tax purposes only with the HMRC). If you can do them both at once then it would only be for companies which expect to have a large income from the start.