Pros
None, unless you are Spanish and have family in senior management positions - in which case you will already work there.
Cons
The company has no staff development strategy beyond a nepotistic promotion and recruitment policy for Spaniards and condescending everyone else. The management are arrogant cowards that will neither take advice from the people they employ to provide guidance or responsibility when things go wrong. The supply chain consists of Spanish companies shoe horned into the British industry meaning meetings will frequently descend into an entirely Spanish discussion with no regard to the English speakers in the room - fine in Spain or South America but a little rude in the UK. The company has very few of its own systems or work practices and relies on those in its joint venture partners, it then blames them for any failings - Spaniards are never wrong. There are no benefits if employed on a UK contract, those on Spanish contracts will have their rent in Chelsea or Earls Court paid, flights home, private healthcare, expenses. Essentially if you're British you're a second class employee and should never forget it. Engineers have been instantaneously sacked for not arranging taxis for certain individuals in the company that it is widely believed can walk on water.