^^ with a blue badge you can park on double yellow lines anywhere as long as you are not causing an obstruction.
if you can park without paying in ordinary bay depends on the rules for the particular car park. Some say Blue badge holders can park free anywhere, some say only in disabled spaces , some say everyone has to pay disabled or not and only provide the bays. There is nothing in law to say disabled bays have to be free , just that they have to be provided.
So be safe and free park on a yellow line!