I first came accross the 1984 Data Protection Act in the late 80's and it was a hefty tome them.
Now it's been updated and amended so many times even police forces have problems understanding it. (Remember how Ian Huntley got the job of school caretaker even after police were aware that complaints of a sexual nature had been made against him).
Now, unless there's someone who from a previous occupation was 'forced' to study this weighty manual; I don't think you're going to get a proper reply.
But as long as you use your common sense on keeping only the information regarding your customers that is necessary; and ensuring that the data is kept safely and old worksheets are destroyed before disposal; then you're not going to have any problems.
The regulation is there to protect people and their privacy; not just to create mindless red-tape to bog down hard-working people like yourself.