The master bedroom laminate had at least two obvious problems. By the chimney flue, the floor was flexing significantly, and by the built-in wardrobe, the floor was butted so hard to the wardrobe it was tilted upwards.
My friendly builder showed up this morning, chippy in tow. Off came the skirting boards (with bare hands even, the job was so poor), and up came the laminate. We found missing underlay, underlay overlaid on underlay, and under the underlay, a nail, a screw, bits of plaster, and an off-cut of laminate.
Don’t ever give MNP Flooring business.
Random ends of underlay, some overlapping 
More of the random ends 
An off-cut of laminate, from under the underlay 
A nail, from under the underlay 
Gaps in the underlay, not taped 
A screw, from under the (expensive) underlay 
Underlay on underlay 
More missing underlay, and the board was butted to the kickboard (barely) instead of taking the kickboard out and fitting the laminate underneath 
More underlay on underlay
Unfortunately, we won’t be putting the flooring back down, because the roof is leaking 🙁