Recently, I needed some plastic bar, and looked high & low for suppliers, who weren't in China a month away, or having to buy a metre or more for £40+. The usual model engineers' suppliers didn't have what I wanted, and I found some likely items at a custom car company, but at 10x the price. Finally, googling 'engineering plastics' led me to Direct Plastics in Sheffield, which answered my prayers. Lots of materials, in short lengths, for reasonable prices, data sheets, technical help, advice, what could be better? I'm going soon, I hope their service matches their website. (Usual disclaimer)
Geoff