Or better still use the resident HR advisors on Answerbank?
Under TUPE, the new company has to transfer you under the same basic T&Cs of employment, however the problem here is going to be whether your existing bonus scheme is contractual or not. TUPE doesn't protect you from the loss of your job through redundancy (though some people seem to think it does), it does protect you from changes to your conditions of employment. So if it is 'acceptable' now to operate at 76% of target levels (albeit without earning much in the way of bonus) without your job being at risk of dismissal, I don't believe that it can suddenly change to it being unacceptable under the new employer. To dismiss you, the dismissal must be 'fair' (fair in the eyes of the law as distinct from being just) - and that doesn't sound fair to me - Any attempt at dismissal for not hitting targets would have to be on capability grounds and the company would need to take you though a Warnings disciplinery process first - that takes time because you need adequate time in which to improve your performance.
As to whether they could make you redundant after 3 months, this sounds very dodgy. As a franchise-holder you would not be an employee, surely, you would be self-employed. So they appear to be threatening you with redundancy because the business activity is ceasing, because they have decided to change the business model to employ only franchise-holders? Very dodgy. Try talking to ACAS or CAB, as Ahm suggests.