Under the provisions of the EU’s Free Movement policy, any EU citizen can live in an EAA country providing they can demonstrate that they are exercising Treaty Rights.
In practice, few countries properly police this, for example if you are a French national living in London you are under no legal obligation to apply for a residence permit. So the UK Border Agency actually have no idea any many foreign nationals are in the UK.
The Spanish economy is falling apart and in a bid to get rid of non economical migrants the Spanish government has announced a tough new set of restrictions on immigrants from other EU nations . If an immigrant cannot demonstrate that they are financial sound, the Spainish state that they will be deported and and estimates it will save £800 million per annum.
Currently over 790,000 British people live in Spain. Will the UK government start to ‘police’ Spanish nationals in a tit for tat move if British citizens are forcibly removed?