I don't know the exact details of the case so can't say too much, but I'd like to make a couple of points.
A couple of years ago I accepted a job as an FO for a bizjet company. The package was made up of a lowish basic salary plus reasonable flight pay (fully taxed) making a total package which I was happy with. The more I flew to more the more the company earned and the more I got paid. I accepted that when I signed the contract.
The legislation passed by the government regarding holiday pay I'm sure was to protect lowly paid workers (i.e. shelf stackers) from being taken advantage of. It was never intended to benefit well paid professionals such as pilots. If the legislation was brought in whilst I was employed (sadly now been let go) it would never have occured to me to go back to the company and renegotiate my basic salary.
I don't know if MPs get an attendance allowance, but I'm sure the House of Lords do. There would be public outcry if the Lords used the legislation to claim extra holiday pay!
Does anybody know if the case has finished and what the outcome was??