"in the UK the Information Commissioner has made it clear it won't be heavy-handed with fines"
Unless the information commissioner is immortal and is appointed for life there are no guarantees that this will always be the case. Companies read the law and see that they can be fined up to €20 million or 4% of their annual revenue (whichever is greater) and act accordingly. The GDPR is especially pernicious as its scope reaches beyond the boundaries of the European Union. If you're an American company and a single European citizen uses your services you are bound by the GDPR's regulations.
Some people claim that the court system in the EU is more judicious than the United States. For those people I want to ask "Why should I trust the opinion of the people who are going to sue me if I am found to be noncompliant". If you think the people covering their butts are being irrational, read the law again.