The problem with Shariah Law is interpretation. The principles as stated above are fine and moral. But once you leave the regulated genre of banking it gets more and more down to who is pronouncing what is and isn't law.

There have been calls for Shariah Law to be incorporated into UK jurisprudence. Neglecting the fact that there is a perfectly workable system called Tort Law. And you can always draw up a contract between the parties. The Islamic Banks do that by inference, you deposit or borrow on their terms, available in writing on an obscure page behind a button on their website.

When it comes to mortgages, it is fine when it is fine, but when people fall on hard times, morality is hard too. The banks have to protect their interest just the same.