You can complain to the
Advertising Standards Authority about adverts on the internet, I have done this. The ASA will assess the advertisement for breaches of its code. You'd need to inform them how the advertisement had misled you, so you'd probably need to purchase a product and demonstrate that it was not as advertised before making a complaint.
Ads on Facebook can be reported to Meta, but in my experience all that happens is a few days later you get a reply that the ad doesn't go against their community standards. I think that Facebook's "standards" should comply with UK legislation - in adverts and everything else - but sadly that isn't the case.
