The UK transcribed the Regulations into its own law when leaving, because that allows to delay the tedious work of figuring out which rules, if any, should be modified, or eliminated for the UK itself going forward, something that in principle the elected politicians would obviously want a say in but there's always something more important.
The UK had anyway had similar rules prior to even the Directive, in the form of the Data Protection Act. More modern rules change some of the details, but the general thrust has been consistent, you should not have data about people that you don't need, and unless you have some compelling reason not to ask (e.g. detectives obviously won't be telling somebody they're collecting evidence that they sell stolen goods) you must ask permission before you store data about people in the first place, and people have a right to ensure your data about them is correct, which necessarily means they have a right to know what that data is.
The first Act cares too much about exactly how you store data, so that a filing cabinet full of information about people ends up not captured, while an Excel spreadsheet is. In current legislation (and the GDPR) you can't get away that easily. If you write all those records by hand, then shove the piles of paper unsorted, into an old shoebox and put it in a broom closet, then they're not subject to the rules, but they're also now pretty useless to you. The moment you arrange to make them easily accessible so that your business could benefit from having these records at all, they get captured by the rules.