While the focus is on social security contributions, tax issues are also at stake: Because contractors invoice their clients, they are subject to VAT and often have claimed tax breaks in relation to VAT - which they are not allowed to if they are in fact an employee.
For the record, Ryanair has released a press statement that they are not investigated. The problems lies with Brooklands because if there is an employer, it would most probably be Brooklands and not Ryanair (or is Ryanair invoiced for the services by the pilots rather than Brooklands?)