Please could you advise if there is a statutory provision relating to a change of payroll date in the context of a change in terms and conditions for TUPE (and other) staff. I am sure there is some form of exception for change in payroll date, but cannot find any relevant information on this.

The date on which staff are paid is usually a term of their contract. For example: "Your [basic] salary is £[AMOUNT] per year which shall accrue from day to day and be payable [monthly] in arrears on or about the [DATE] of each month directly into your bank or building society account."

Technically, if an employer wishes to change the date on which an employee is paid they will need either to have that change authorised by the contract or to take steps to vary the employee's terms. 

However, in practice, as long as an employer gives employees sufficient notice of the change of pay date (so that, for example, they may change standing order dates) employees are unlikely to take any action