"Taken over" might be a bit of a sensationalist way to put it. Rather, the trust purchased the book shops in agreement with the SPCK. They still maintain the relationship and will carry SPCK publications, as well as material for Catholics, Anglicans and other Christians. It has improved the availability of Orthodox materials - that is the major boon (Orthodox books and icons.) The 'big controversy' is that they no longer sell the Koran, and the new owners have encouraged other Christian bookshops to do the same. SPCK and its Press still remain Church of England.
I was in the Westminster branch last month - very nice bookshop. Right above Watts of Westminster, and next door to Wippell's. Even more important was the Antique books section. If I had the cash and the luggage, there were a few items I would have liked there.
The St. Stephen's Trust, as I understand it, was founded by a few Antiochian Orthodox laymen from Texas (converts from ORU, as many others of us were.) So far they've purchased one redundant church - and that in a Muslim neighborhood. Redundant churches tend to get turned into residences, balloon shops or antique warehouses, sometimes mosques, Hindu Temples, or Pentecostal churches. So - Orthodox church isn't such a bad trade (though, God be with them in doing mission's work in a Moslem neighborhood!)