I use almost exclusively Seawhite of Brighton's range. I like their square ones the most and I think it is their chunky shape and size that appeals.
A little bit about Seawhite - this is what they say:
For more than 30 years Seawhite has been supplying the UK educational market. Our strong reputation has been developed through our use of innovative and quality products backed up by a personal, fast and efficient service. Products such as our sketchbooks and polyholdalls are now used in schools, colleges and retail shops throughout the UK and increasingly in Europe. Still a family business, our 50+ strong workforce has helped us achieve steady growth every year. Seawhite is based in Partridge Green, West Sussex, not far from Brighton where the business began. Our modern offices and large warehouses enable us to keep a large stock with a quick turnaround. On the premises we also have a well stocked factory shop and Seawhite Studio - a modern painting studio with art classes run by Emily Ball. We also have a manufacturing and warehouse facility in Worksop, Nottinghamshire, expanding our philosophy of "made in Britain" where possible.
Ideas for branding sketched into sketch book before being drawn up in Illustrator.