For anyone worried about coinbase etc there are people that have hundreds of thousands of not millions sat in their accounts. Coinbase is about as safe as it gets when it comes to crypto exchanges if you set up your 2FA aswell.
Do not ever reply to ANY emails that are about your account no matter how genuine they look. I’ve had accounts with multiple exchanges for 5 years and never had a genuine email asking me for info other than confirmations and identity docs when first signing up.
Yes they will go offline for ‘maintenance’ during any kind of big jumps in price, binance is specially bad for this. But it’s just games they play.
That said no matter how safe exchanges are it’s always better to have your coins in a wallet where you are the custodian. You are probably going to be ok with smaller balances below £10k, but if you’re planning to go big then your money is in their hands really.