Anyone have advice about cocaine

Doing it is always a risk because you never can guarantee it's actually just cocaine no matter how much you trust the person supplying it. I'd recommend not mixing any other drugs and have narcan (Naloxone) handy if possible and make sure you have a friend you can trust if things go wrong to help. I'm not sure how prevalent fentanyl is in the UK but it gets on everything here so just be careful because you can wind up dead and it's simply not worth it.