Mark, I used to be a mortgage advisor for my sins and my understanding is that if you keep any personal data of customers either on computer or paper you need to be registered for Data Protection, costs between £30 - £40 per year if memory serves me correctly.
Think there's a bit of difference between:
name, address, phone number, type of carpet
to
name, address, phone number, employer, bank account details, income, out goings, DoB, driving license details, savings etc etc
Under your conditions everyone with a mobile phone and/or pc would need to register which is plain stupid.