I'm heading back to Ireland next week,if its small and light I can take it for you and post it from Heathrow.
Other than that the Argie postal system inst so bad sending stuff out.Just make sure to register it..It will osund high in pesos but you have to think of the distance you are sending it.10-15 days to get to the Uk.From the Uk can take 10-45.
correo argentino is fine, its reliable, tracked and affordable. We've sent loads of stuff to the UK without incident.
Sending stuff out the country seems to be ok, its more of an issue getting stuff in due to the intervention of customs agents.