I would think that within Europe at least you can travel without any fear of being hindered or questioned, so long as you have a marriage certificate with you where the child's surname and his (assuming the child carries his name) links all three of you together in all three documents. In some countries it is customary for the wife not to change her name (why should she ?) so your maiden name would be no problem unless you come up against an ignorant/obstreperous official (his problem). In some countries husband, wife and children do not share a last name and siblings of opposite gender do not either - these people travel without being challenged. If you have problems then they can just as easily be in Britain as anywhere else. As an added precaution, you might take with you the child's birth certificate which, together with the marriage certificate will amply demonstrate your familial connections, albeit with you presumably under an acquired alias..