Tha fault is entirely yours IMO, you issued signed instructions to the BOS to pay money into the designed RBOS account. I would write to RBOS (not phone, you need a record) and ask them to contact the account-holder who's received your money, and ask if they will refund it to you. I don't know what the precedent is in this case but it's worth a try. Unfortunately a standing order is set up by the originator so it's up to you to make sure that the details are right in the first place - and incidentally (if you haven't yet) you also need to instruct BOS to cancel the wrong s/o now too, that has to be done by you too otherwise any future payments would be wrong too.