A good post Baz, I feel much the same way. Many are quick to question the need for the UK to retain such capabilities 'in the current environment' or 'in today's world' or other 'clever' phrase.

They are united in their disregard for both historical precedent and the uncertainties of the future. Some claim to know what the future holds "We won't fight wars like this in the future..." and other tosh is bounded around to justify the latest cuts or'adjustments. If the future was reliably predicted in the aftermath of the Cold War then we would have retained a larger force all round, had more attrition replacements ready, larger fleets to spread fatigue with equipment suitably modified for desert ops, stockpiles of desert kit, ammunition etc. What really happened? We made assumptions that proved to be wrong, flogged off kit, reduced stockpiles and trained strength and got shafted.
We may not use a capability for years but it is there, as Baz says, as a deterrant. If the deterrant fails then the array of capabilities keeps options open for commanders to chose the most effective (read lowest casualties) for a task and also keeps the enemy guessing. Thus, although the Paras may not drop on the day (and thus are not seen to 'do any work'), the enemy's forces have been divided - guarding against this eventuality. Likewise they may have been worried by the Booties threatening their coastline - divided again.
The ability to divide and fix (maybe not the accurate description of this effect but close enough) the enemy in this way can save us casualties even without employing, say, the Paras directly in the action and ensures too that we retain the ability to surprise. Of course, to be an effective deterrant the force providing the capability must be stood up, trained and kept at readiness - it must be seen to be combat ready... reducing the number of training drops may not suddenly remove the capability but it is a slippery slope and one difficult to reverse - it should not be allowed to happen.
To me this is a situation seen across the forces in one form or another, it's just that the Paras are more in the public eye and the stats for number of jumps are easier illustrate to Joe Public. I am certain that many other areas of capability have suffered due to the lack of time available for suitable training between tours.