If you can get legal advice, the time to get it is when dismissed. If they've made an error that is the only point at which it is actionable - any advice before that is speculation. It is also the only time at which a no win no fee lawyer is going to assess it. They have a useful function, if for no other reason than if they won't touch it you probably don't have much of a case to argue. If there's money to be made, they'll take it! Just be careful what you sign up to if you go down that route. The devil is in the small print.