Contacttower: 24 months - same as for SEP Class Rating so that both could be conveniently revalidated during the same LPC.
Revalidation by Test only.
IO540 - the problem is that different EU nations have different airspace regulations. What is lawful in one may not be so in another. I suspect some of the rules are left over from the Cold War - so that intercepting, identifying and reporting off-airways aircraft would less difficult, perhaps? So it'd have to be up to the individual authorities to decide in which airspace a Class 2 IR would be 'permitted'.
I don't know why you didn't receive my e-mails - they went to the addresses you gave me!