Personally I like the contrast of the rogue coloured tiles, but I can understand that you may prefer a uniform look

Ian - the problem is that without the correct UV stabiliser in them, the tiles will beome brittle and will fracture/disintegrate over time as well as further lighten in colour. Recycled plastics are all very good and environmentally responsible IF they are formulated correctly.

Tim - if you read this, these are (I suspect) the same tiles you have on your new conservatory roof (they are what the company we both used use as standard), and yours were installed at around the same time that the tile manufacturers had this batch problem, so do keep an eye on them.

I've read it (thank you!) and been outside to check. All looks good at the moment. We had a terracotta colour, which might make discrepancies more difficult to detect. We'll see!

Tim - it becomes apparent very quickly once it starts happening - but only shows when it is dry not when it is damp or wet. It might only have been the 'black' (which are actually dark grey) ones, or it might have been an employee who got the recipe wrong on different batches of different colours. As you say, we'll see!