I think we are at cross purposes here. I was responding to the assertion that unions are there to protect their members' interests, which I don't deny.No, you said most, but didn't specify which were and which weren't illegal.
As for what is and isn't illegal: Apparently without unions, companies would be "forcing staff to work 7 days a week on minimum wage with no breaks, 12 hour days".
The EU Working Time Directive, incorporated into the Working Time Regulations, specifies rest of at least 11 hours in any 24 hours; restricts excessive night work; and makes a default right to work no more than 48 hours per week. A worker is also entitled to an uninterrupted break of 20 minutes when daily working time is more than six hours.
This may be easier to enforce with the help of a union, but the law applies to union and non-union employees without distinction.
IIRC, the UK negotiated an exemption to the absolute 48 hour maximum set out in the Directive because unions didn't want their workers to be denied the ability to work longer hours through overtime.