I’m wonder what sort of disabled parking bay it is because if it’s one where the road has a white lined boxed with “disabled” written in it then AFAIK anybody can park in these spaces with or without a BB and has been brought up here and other forums about these types of spaces being next to useless.
On the other if it’s one of the spaces that has a post at the side of the road saying “Blue Badge only” then you must display the badge. If its this type of space, even though there rare, then the fine must be paid if no badge was displayed.
Could be completely wrong because I’ve never used that sort of space as I always feel those spaces outside someone house is there for a purpose and could cause a lot of problems for the person who lives near by if I were to occupy such space.