Default [Q] Problem with Spanish SIM in unlocked phone

Hi all,

I've just moved to Spain, and I'm having trouble using my phone (Nexus 4) and my girlfriend's (Moto G) on a Spanish network - we have pay as you go SIMs from Euskaltel.

I can't for the life of me work out why we're having problems - both phones were unlocked back in the UK and I've successfully used a number of UK SIMs (again on both phones).

There are several "symptoms" I'm seeing:
1. Every time I restart the phone with the Euskaltel SIM inside, I have to enter the SIM PIN code. This seems unusual.
2. When I went on IMEI.info to check whether the phone really was unlocked, it lists the Network as UKG and the Carrier as UNITED KINGDOM_OPEN. I wonder if somehow our phones are only unlocked for UK carriers? I didn't realise this was possible, but if it is, how would I remedy it?!
3. When I try and download the Euskaltel app from Google Play, I'm told that it is incompatible with my devices. Perhaps caused by the previous problem?
4. I can make emergency calls, so it's not a connection problem but rather a registration issue.

I'd be very grateful if anyone can shed some light on this!

Many thanks.