Wil Freeborn is an illustrator and graphic designer based in Glasgow, Scotland.
Though his professional portfolio focuses on his (quite nice) graphic design rather than illustration, his blog features a number of wonderful sketches.
These are of a variety of subjects — cafe and store interiors, schoolrooms, townscapes, landscapes and a particularly nice series of people working on a steam locomotive (also here). There are also life drawings and pantings and a few other projects mixed in.
Most of his sketches appear to be in pencil and watercolor in the pages of Moleskine sketchbooks. They combine the informal, loose qualities of travel sketches with clear observation and occasionally more elaborate rendering in watercolor.