Unless you are already experienced in cryptocurrency, I recommend that you use Coinbase as your exchange for transferring fiat currency from and to your bank account. If you use my referral link, we will both receive $10!
You will need to provide all of the standard information for ID and address verification since it is fully-regulated. In the UK the regulator is the FCA, similar to a bank.
Once your Coinbase account is set up and verified, I recommend that you use Coinbase Pro for all of your transactions in and out of crypto. Although the interface appears to be a little more complex, it is just as simple to use as the regular Coinbase and commissions are much smaller.