I would think the situation with regard to deployable devices in the UK in the mid 50s was similar to that in the US in the late 40s or the USSR in the early 50s.
On the other hand, 25 Blue Danubes in Valiants or Vulcans could have made a very considerable mess of Russia.
Another factor is the way we view nuclear weapons today is different from the way they were viewed in the mid 50s. 25 Blue Danubes would have been regarded as a very considerable deterrent then, if not now.
There's no real evidence that nuclear weapon deployment diminished as a result of Grapple. The Violet Clubs/Yellow Sun Mk I devices were of an order of magnitude greater than Blue Danube, whatever might be said about their safety.
On the other hand, the USAF deployed some very similar devices in the early 50s, although I think the safety device was chain rather than ball bearings.
To single out the UK for an inadequate deterrent is unfair. Perhaps a few years later than the USSR, but not by many.