May I ask: By "Full residencia" what do you mean? You do have to renew still, right? The reason I am asking is because we too are not from the UK so our situation got complicated as well due to lack of clear information. The more we asked the worst things got. We made lots of trips by bus back and forth to Murcia & Cartagena, sometimes spending nights in hotels.
To our surprise, after the first authorized Residencia we thought things would get easier by the renewal time since we had provided, starting in Spain Embassy in our country of origen (USA) all the paperwork required from us.
There's a 3 digits (? 060) ph number that is very helpful and customer service is actually very nice and helpful. If any questions call this number. It's a Government service number. The reason for the Residencia is to be able to spend more than 90 days in our home in Spain. Flying back and forth every 90 days became very expensive for us. Plus the fact that our pension gives us way more quality life in Spain more than it would in the US. Thank you.