I remember being pretty daunted by the squeeze descriptions the first time I went through, and was rather relieved when I finally got there - and this is before the so-called 'clearance'. If it had been solid rock it may have been different, but as with all squeezes, you either fit through or you don't, but there's no chance of getting stuck whatever happens. Just that the return trip from that point would be a bit more tiring! But as you can just dig it out and then refill it, it's hardly a worry. Remember the original PDMHS diggers cleared all of this by hand, and going uphill.
That said, the coffin-level is a painful slog if you're normal height or taller, and I find that to be easily the worst part of the trip. I'd be happier exiting via the 80m Day Shaft than the coffin level personally, but that would mean pre-rigging in advance, and exiting on the farm land uphill, so we've never quite managed that yet. One day I plan to do a reverse trip, if I can persuade anyone - down the Day Shaft and then uphill to the quarry shaft and out that way. And praying that no-one decides to descend whilst we're climbing out! Incidentally, does the usual entrance shaft actually have a name?
As for squeezes in general, the ones going through the Dynamite Series in Carlswark (via the Flower Pot entrance) are pretty good training - both for contorting one's body and for maintaining a 'calm outlook'. The Iron Maiden in Perryfoot Cave is still the scariest squeeze I've ever done - I chickened out the last time we went in there, even though I'd passed it before. But it was so traumatic, I decided once was enough.