Thanks for the replies, I've got to the bottom of it now. I left a message on the gocardless phone and they returned the call this morning.
Turns out I donated £50 to a local group that were raising money for a splash park for the kids. It was a few months ago and the deal was that if the group raised the target amount by the deadline date then they would debit the amount from the donors account.
what I didnt know was that they were using a middleman (gocardless ltd) to collect the donations and thats why they debited my account, They just didnt reference the splashpark on it. It's all good now.
Incidentally, I dont have my account details on my website, just on the slips I put through the door after cleans.
Regards
Adie