Yes Ryanair is with Balpa as far as I know. They are also with SNPL in France and Anpac in Italy. Ryanair changed their attitude towards unions in the countries they needed to. Other countries they’ve then created low-low cost subsidiaries on some of the worst conditions in the industry. This is where Buzz and Lauda come into the picture.
Again ALL reasonable contracts offered in Europe today have union backing. Yes the LGW BA contract is not great but it is still much much better than Lauda or Buzz and wasn’t it also an option to stay on fleet as a FO in LHR and wait for command? The guys I know that took command in BA had only just joined the company.
The companies you mention that have little to choose from are all unionised except for Wizz