I’ve had the Halfords ones for years, can’t really fault them for what I paid and how long they’ve lasted, but here goes.
1/ over time they’ve expanded, IDK if that’s as a result of all the standing and walking on that’s been done, or whether the odd solvent spillage (white spirit, or Screwfix No-nonsense) has swelled them but means they now are not a perfect fit and pucker a bit. Which leads to
2/ although I shove them back down as best I can the interlocks are not tight and where it’s not a clean garage muck and dust gets in the gaps which is a pain to have to lift the edges to hoover out
Like I say, for the cost I should just bin them and get a new set and they’ll be grand for a couple of years at least but instead I bought an Amazon barrier mat which sits over the foam mats – not thick enough to be able to work out there barefoot so it’s over the foam mats but has no gaps, and can be easily lifted and taken out the front with a whacker every now and then to clean it off. And I’m more careful now with solvents too.