But the opposite argument could be made: look, our British security apparatus is so good, that 1) other countries are being hit, despite "us" being much more involved in topical overt conflicts, and 2) "we" pretty much know right away who caused what (see response to the bombed Russian plane). Clearly they are working fine as they are and they don't need any more powers.

In fact, French and Russian security services are known for their heavy touch. Fat lot of good it's doing for them.