Can I opt back into the 48-hour limit?

Yes, you can write to your employer at any time saying that you wish to regain your right to work not more than a 48-hour average week.

When you signed an opt out, it may have contained a clause saying how long you would have to wait before the rules applied again once you had reversed your opt out. This waiting time cannot be more than three months.

If your opt out agreement did not include this kind of clause, then you only have to wait seven days before working time rules apply again.