Interesting info from my accountant. His feeling is that there is a risk. However HMRC apparently take a practical view of the arrangement regardless of the complex setup to avoid an employer's obligations. He tells me that HMRC are likely to take the view that any Ryanair pilot employed by Brookfield and based in the UK under the old contract, is in effect a pilot working indirectly for an Irish Company on Irish aircraft. IR35 is therefore unlikely to impact on current arrangements as it only affects British companies.
Whether that is accurate or not is anyone's guess...