Go Cardless is a way of allowing businesses to accept direct debit payments without having to meet banking requirements for taking such payments from customers' accounts directly. (i.e. Go Cardless has convinced the banks that it's a reputable company. It them acts as a broker so that other firms, who might not be as able to meet stringent banking requirements, can accept direct debit payments through them in return for a fee).
If you're seeing 'Go Cardless Ltd' on your bank statements it doesn't mean that you're paying anything to that company itself; it simply shows that another firm is using Go Cardless to collect direct debit payments for them.
So you need to ask yourself whether you've actually signed up to anything which costs £8 per month. If you can work out what it is, and you're happy to continue with the arrangement, then there's obviously no problem. Otherwise you need to use the Direct Debit Guarantee to get your money back:
https://www.directdebit.co.uk/DirectDebitExplained/pages/directdebitguarantee.aspx
(See the links down the left about 'Cancelling payments' and 'Incorrect payments').
You can find out where your money is ultimately going to from here:
https://gocardless.com/payment-lookup/