Might be better for you to talk to a UK dealer who is prepared to ship to Europe then - or consider organising your own courier pickup. Would probably get to you in the same time as one posted normal mail from Madrid.
Put the other way round - I work in the UK with machinery from European suppliers and I can place an order with them at 2:00 pm (ex Austria or Germany) for delivery at my workplace 9:30 the next day. Priority costs extra - normal delivery gets here mid afternoon. For the equivalent to a key fob I would expect about £15 normal or £25 priority tops.