I am not a solicitor but I am an accountant with experience of company formation. I am willing to arrange this for Wikimedia UK (whether or not I am on the Board) if they want - the only cost will be the £20 Companies House registration fee. I know a friendly JP who has agreed to witness Form 12s for me in the past so that shouldn't be a problem.
Not being a solicitor I can't offer any advice on any other legal matters.
regards,
Andrew Turvey