Forstater will still be crucial. There may be a breach of data protection going on here but there is also discrimination on the basis of a protected belief.
I would be really surprised if the club try to contest the legal action. The law is now crystal clear: under the Equality Act, you cannot discriminate against people with gender-critical beliefs. After the Forstater precedent, we saw wins for Allison Bailey, Rachel Meade and Jo Phoenix. Perhaps more pertinent for this case, we saw two organisations - the Stand comedy club in Edinburgh and Nottingham City Council - back down when threatened with legal action after discriminating against women with gender-critical beliefs (Joanna Cherry and Julie Bindel).
I imagine Newcastle's lawyers, if they are remotely competent, will explain to them that they need to issue an apology immediately and not attempt to fight the legal action.
As for the Data Protection Act, I'm less clear about that - you'd imagine it breaches some law or other to follow people around and record information about their movements, but who knows?