Some suggestions https://www.expertreviews.co.uk/garden/1414274/best-composite-decking.  Get samples to compare.

Thanks Sarah! This article is so helpful!!

I think to be able to make a good choice, you need to know of the disadvantages of composite decking, as well as the advantages. When I researched it a few years ago for a new patio, I was shocked how many problems there can be. It can warp, fade and split over the years, way before the guarantee period. In fact in the USA, where they love a deck, customers are suing manufacturers as the product does last as long as suggested. The product is a mix of plastic and wood along with glues. It can get extremely hot in warm weather. If you go to this website it will explain more www.ultradecking.co.uk. Im not trying to put you off, but I think you just need to be aware. Porcelain, Indian sandstone or hardwood may be a better choice?

@Sonia Thanks for your feedback, and the link! I'm looking into it.

Hi Jane, I've used Trex Composite Decking for my deck, wooden frame underneath needs treatment though. Also, ensure the installer uses plenty of support underneath as mine has bent after 1 year already due to not having enough supporting frame. I used composite decking before and was happier with UPM decking. I know that Millboard is high-quality but pricy. Good luck!