Energa evidently Wanders:-
https://en.wikipedia.org/wiki/ENERGA..._rifle_grenade
As to the PIAT it would seem to me to be an elegant (!) solution to the airborne troops dilemma, how to take into battle a lightweight (ish) weapon that could deal with tanks. OK it had its limitations, not the least of which was the suicidal short range of its effectiveness, but given the technology of the time it was as good as could be reasonably expected in my view.
Market Garden failed to outflank the Siegfried Line to the East or the German troops in the West bottling up Antwerp in the Scheldt Estuary. It also failed the population of the Netherlands who endured a winter of starvation that killed tens of thousands of them. If the co-ordinated effort that ensured the success of D-Day had been repeated in the planning and execution of this Operation it could have succeeded. As it was, XXX Corps got tantalisingly close to the southern approaches to the Arnhem Bridge. Was it really too far, or were we too slow?