In 1965 Monsieur Guy Demarle, a French baker came up with what he called the Silpat™. A mat made out of woven fibers and silicone. The fibers giving shape and strength and the silicone providing a remarkable nonstick surface. It did him well and he became one of the most famous baguette bakers in France, no small feat. At the same time his Silpat™ mats went crazy and sold like... really good baguettes.
Well patents last at a maximum 20 years, so come 1985 and people started copying and ripping off the Silpat™ mats. And that my friends, is where we find ourselves today. In a weird world of a million different brands of nonstick baking mats.
True to their pursuit of quality, quite a few of the early seasons seemed to feature the Silpat mats for the bakers. They're fairly distinguished with a bold orange border, chamfered corners, and "Made In France" proudly stamped on them. In the more recent seasons this is not the case.
Now The Great British Baking Show nonstick mats are made by various random brands and come in various styles. I've paused the show, inspected brands, and then searched far and wide for them, they're random, and in many cases fleeting.
The mats all serve the same purpose - to keep bakes from sticking to the pan. This is most effective for things baked on sheet pans, such as cookies and loaves of bread. The silicone does not bond to the baked surface and allows for the bakes to easily release. Raw and uncooked sticky things will - and to the baker's dismay - do stick.
The mats at this point in time have all sorts of utilitarian designs on them. Some have pre-drawn circles for cookies on them such as the Silpat Perfect Cookie Baking Mat (Amazon Link (UK)). Others have concentric circles on them to help roll out pastry to a given size such as the Silpat Perfect Pastry Full Size (Amazon Link (UK)). Do be mindful that the pastry mats are full sheet sized!
Since the patent is long gone for Silpat Nonstick baking mats (Amazon Link (UK)), it really depends on the quality mat you want, and the money you want to spend. If you want the best quality and the nicest mat go with the Silpat options. They're original, and great.
If you're looking to save some money Amazon Basics silicone baking mats (UK) are $12.45 for 2 of them. These clock in with 83% 5 star ratings out of 47,000 ratings. Additionally Amazon Basics makes a 3 pack (UK) with various size mats. Being that they're made by Amazon, I trust they have a decent build quality, and won't fall apart within a few days.
If you're looking for the mats with designs, Amazon has some really affordable choices for both the cookie sheets (UK set) as well as pastry sheets (UK). Again be mindful of the size of the pastry sheets.
All in all if you're looking for the original non-stick baking sheet and have the money to shill out for them, the Silpat Nonstick baking mats (Amazon Link (UK)) are the way to go! If you're looking for the exact same thing with a different design, the patent ran out years ago on, Amazon Basics silicone baking mats (UK) are an easy and ridiculously affordable choice.