The number of Muslims in the UK is the other way around, 5%. But I digress. The point is, if the US Gov is legally restrained from spying on its citizens, they will just get the British Government to do its dirty work for it, and vice versa. I don’t think there is any real way to stop western governments from engaging in unethical eavesdropping unless they are forced to make international treaties preventing each other from spying on each other, and frankly, I don’t see that happening, because it is too convenient for both of the Governments to be able to do so.
Spying on islamics should be priority #1.
The splash side effects have to be contained and be considered scandals. Collecting all records and decrypting all 1024 bit RSA (they will surely this) and then 2048 RSA (At Utah) are the real problems.