No ones selling oblong paving slabs, it seems

After some intensive online research and a wander around B&Q (my most hated shop), it seems oblong paving slabs aren't the thing anymore. Well other than at Travis Perkins but I don't think it's worth blagging a trade account or a tradesman for four of them! So plan B...

I need two to finish outside the shed and have some already laid at the far end of the greenhouse, so today I'll be moving those then. Then I'll be working out if they're 450 or 400 wide, I'm hoping 450 as that seems to be the size of choice and working out how many of those I'll need before heading out and buying some!