UK and Sharia Law

The UK has begun to allow Islamic Sharia courts to act as arbiters in civil family matters/disputes:

The government has quietly sanctioned the powers for sharia judges to rule on cases ranging from divorce and financial disputes to those involving domestic violence.
Similar courts have been in existence in the UK within its Jewish community:

Jewish Beth Din courts operate under the same provision in the Arbitration Act and resolve civil cases, ranging from divorce to business disputes. They have existed in Britain for more than 100 years, and previously operated under a precursor to the act.
Unfortunately, the journalism here is a bit mushy, so it is difficult to know exactly what is going on. First, I think there needs to be a distinction between civil and criminal cases here. The first quote above mentions domestic violence. Is that a civil matter? Isn't it a criminal one? Elsewhere in the article it states
Siddiqi said he expected the courts to handle a greater number of “smaller” criminal cases in coming years as more Muslim clients approach them. “All we are doing is regulating community affairs in these cases,” said Siddiqi, chairman of the governing council of the tribunal.
So it does seem that the intention is to have these religious courts cover certain criminal cases as well, if not now then in the near future. If indeed the UK is ceding criminal authority to these courts, then this is a stunning development. Can the UK continue to exist if there is a state within a state, with a separate legal system and separate criminal codes?

Even if the system in question is for civil matters alone, I would have serious reservations. Is arbitration legitimate if the arbiter has a pre-existing bias against one of the parties? Is it legitimate if the parties do not have equal rights before in the court? It's no secret that Islamic law treats men and women differently, their rights in Sharia courts are not equal.

Ideally, parties entering arbitration do so willingly and voluntarily. But I suspect that many women who are the victims of abuse would not be in a position to demand a hearing within the existing UK court system, due to family and social pressures.

I would like more details about this. I wonder how the people of the UK feel about it.