I'm glad to hear you're considering joining the QuickBooks family. You've reached the US section of the site here, I'm gonna direct your question to the UK Community so as to ensure you receive the best possible assistance.
Thanks for reaching out, cheers to a safe and productive week.
Yes you can connect your First Direct bank to the banking section in the Quickbooks Online, you can then use this tool to add transactions to the Quckbooks it will just require you to categorise them as regards what income/expense category you want them to be under ( this does have a background memory so next time you select same supplier/customer it will remember the category)
You can also use the banking tool to match to transactions if you are creating the transactions in the Quickbooks it will match to them and make payment/recive payment on the invoice/bill etc which is a helpful tool for reconciling, more information can be found here
The subscription is a rolling month subscription, there is also the option for a free 30 day trial.