Does Aeromadrid offer any conversion flight training?
Check their web site or give them a call. They might not advertise but usually a school will accomadate, they want your money.
Will the UK CAA ground school be accepted in Spain?
No, their web site states Spanish ATPL, well it did a few weeks ago.
Do I qualify for a reduced hour flight training syllabus under Spanish JAA?
Don't know anything about this one. Don't use UK CCAA as a guide to Spanish rules. The Irish authority is very different to the UK. As I understand it there is a reduction in the minimum required hours under JAA but each country is different.
Is the language barrier a problem for any students who trained in Spain?
Friends flew in Jerez and only had problems with ATC. Very little standard terminology.
If I was converting I think I'd liek some flying in English speaking airspace during my conversion.