If you think UK will come through it without firts experiencing “massive pain”, your “understanding is very poor”.
You have some good points but you miss the overall picture.
UK will have massive pains but most of the people will be able to go on with their lives. Some will lose everything and a lot will have to have a more modest life. But this is normal.
Spain will be instead devastated by the economic crisis. they will consume their extra money in no time and then will go into high deficits. The Spanish industry was based mostly on construction and nobody will buy the overpriced and bad quality apartments/houses for a long time.
We’ll talk again in 1 year about this subject, I can guarantee you that UK will be in a much better situation than Spain by then.