With pizza still one of the most popular takeaways in UK ranking in the top three alongside Chinese and Indian takeaways - there are some big players in the market mostly from the United States. The likes of Domino's, Papa John's and Pizza Hut has probably around 2/3 of the whole UK pizza delivery market. These are not the cheapest pizzas you can order, but definitely the quality and consistency beats the competition on most days.
There's up and coming competition from British owned pizza chains like Pizza GoGo, Caspian Pizza and few others which can't compete with the big US brands on the number of franchises, but can certainly compete with the quality of food and the price.
UK pizza delivery market is huge and is also facing a fierce competition from frozen supermarket pizza which has gained more popularity in recent years.