What are your thoughts on safety around 4% hydroquinone products? It appears very effective but I know it’s controversial.

It’s very effective and because it’s a prescription medication you can only get it in the UK if it is prescribed to you by a doctor/ dermatologist/ nurse-prescriber, who I would hope will be a skincare professional overseeing your use of it. If you’re offered anything containing hydroquinone by another route, I wouldn’t touch it.