The purchaser is not required to give details to the retailer; it may be a technical point but it is the retailer which is required by law to give details of the purchaser to the TV Licensing authority.
If you will not pass on your name and address, and they have no other way of obtaining them, they are then obliged not to complete the sale or else face a possible fine of �1000.
I work in Tesco and if the customer has a clubcard then they are not required to fill in a form.
If there isn't a clubcard then a form is generated by the till and the customer is asked to complete it. HOWEVER, no proof of address is required so the customer could write anything they like.