Pieter,
Firstly, congratulations for escaping Ryanair/Brookfield!
I think we flew together from BLQ base back in 2011.
I too have recently made a 'non-standard departure' from Brookfield/Ryanair, and they are persuing me in the same manner. So, you are certainly not the first, and for sure, will not be the last. Funny thing is that not for one second do they pause to think why guys are doing this, and what could they do to stop it....of course they will not bother all the time they are making a profit out of recruiting cadets...but that's another thread entirely.
What I would say is to speak with IALPA. They will tell you that there is a queue of about 30 court cases, between Brookfield and ex Ryanair Pilots to be heard in the UK at the moment. They are waiting to see the result of one case, which is being treated as a test case for all the others. Whatever the ruling on this test case, will probably influence all the others, so there is alot riding upon it. I'm told that the judge is an ex-employment contract law expert and has already been asking Mr Declan Dooney some searching questions relating to the Brookfield contract in it's entirety, not just the notice clause. We all know the contract is tenuously legal at best, as it is so far skewed towards the benefit of Brookfield and Ryanair, but who can call at this stage if justice will prevail?
Solicitors will prove to be very expensive, but consult one if you can. But please speak to IALPA. The more people they know about, the more they can paint a picture of the reality of this contract.
If Brookfield put any form of pressure on you regarding this payment. I would merely advise them, that you are aware of the test case in London, and will communicate with them further, once the ruling has been made, probably within the next couple of weeks.