There are three big marker manufacturers that I know of, Pantone, Prismacolor, and Copic. Prismacolor and Pantone have been around for a long time and I think Copics came out a few years ago.
I have never used or even seen a Copic marker in person, but from what I can tell they seem to blend together well and the finished images have a watercolor look to them, rather than a marker look. They are very popular with people who draw anime. They are also very expensive. Copic marker link. You can look at their (pretty bad) example gallery.
Prismacolors have a good assortment of bright, bold colors. The markers have two nibs, fat and thin. The fat end is very brush like in the way it marks and by changing the way you are holding the pen you can get different line widths. I like the way these big nibs feel, they just glide along the paper. Prismacolor link.
Pantone Trias, made by Letraset, are probably the most widely used marker by professionals. I’ve bought up maybe two-dozen colors over time. Their nibs are a little rougher than the Prismacolors. They have three nibs, fat, medium, and thin. The neat thing about them is you can actually by the ink itself in a refill bottle. Some artists just use the ink and don’t even bother much with the markers, EXAMPLE (Justin Kaufman’s work). Base colors were laid in with the ink refills over an ink drawing and the rest of the rendering was done with Prismacolor color pencils and gouache. Pantone link.
As for paper, there is “marker paper” made by a few companies. Canson is my favorite for paper, Strathmore is another great one. The papers can take a lot of abuse. Bienfang is another company but I’m not as thrilled with their papers. You don’t have to be limited to marker paper, regular sketchbook paper works well too. Just be sure to put several pieces of paper underneath the page you are working on so the ink doesn’t bleed onto the next page. Canson marker paper.
As for buying, you are going to have to look around online for a seller that sells to the UK. Unless you live near a REALLY good art store that is your best chance. Some US based sellers ship internationally but there are the international fees to deal with. http://www.dickblick.com/ This company sells all three marker brands and ships internationally.