For the sake of the cabin crew, let's hope Unite know what they're doing as they've just bet their union on a favourable outcome. Unite are not in a good financial position which means this is essentially a do or die action. If they lose in court on Thursday, they will be paying BA's legal expenses and will open themselves up to counter claims from BA for any losses incurred.
As a note of correction to BASSA's solicitor, you most definitely can be sacked for taking part in a legal strike. It is correct to say that any dismissal would be illegal but there is no right to reinstatement and the level of compensation is limited.
Ask yourselves two questions and think carefully about the answers.
If BASSA's solicitors know that you can be sacked, why are they not telling you of this risk?
If BASSA's solicitors do not know that you can be sacked, how can you rely that any other legal advice they may give is accurate?