Here's a page of links to luthiers' websites. I'll be adding to the list from time to time.

Atkin Guitars Atkin Guitars was founded in Canterbury, England, in 1995. Alister Atkin makes some of the best vintage Martin and Gibson replicas you'll see this side of the pond. Still in Canterbury, now a two-man operation, he builds around 80 guitars a year, each one handmade and completely individual.
Peter Barton Guitars Peter Barton has been making high quality fretted instruments in Addingham, West Yorkshire since 1986. he's probably best-known for his classical guitars, but also makes steel-string flat-tops, Maccaferris, citterns, mandolins and ukes. He also provides an expert repaid and restoration service.
Ralph Bown This website has been 'under construction' for a long time, but don't let that put you off - Ralph is one of the best luthiers I've ever met. As well as the O/OO/OOO classic styles, he makes a range of more unusual guitars, including replicas of the Stellas made famous by blues players like Leadbelly, tiples, harp-guitars and long-scale baritone guitars. High end sellers like Dream Guitars love his instruments, and no wonder. He's one of the very few in the UK who can compete with the very best US luthiers.
CA Guitarworks If you own a Taylor or Lowden, or need any work done in or around Baldock in Hertfordshire, you should know about CA Guitarworks. Chris Andrews has been fully trained in the USA at the Taylor Guitars factory in California by some of their top repairmen. This has made him a qualified Taylor technician able to repair and fit Taylor ES systems and work on Taylor NT necks. As well as being authorised by many more brands, Chris and the team are one of the only repair centres in the UK for Lowden Guitars. CA Guitarworks are also able to set up and repair Parker Guitars and are trained Fishman pickup installers.
Mark Challinor One of the best UK luthiers I've met. His restoration of a Martin OM-42 that had been destroyed by a fork lift truck was little short of miraculous.
Frets.com Frank Ford's website. No contest - this is the most informative website on repair and restoration techniques in the world.
Stephen Hill Stephen Hill has been producing fine classical and flamenco guitars since 1985. During this time he spent many hours in the workshops of Manuel Reyes (Cordoba), Antonio Marin Montero (Granada) and other legends of the guitar making world. He is based in La Herradura by the coast in Granada province, Andalucia, the home of legendary Andres Segovia and the Andres Segovia International Guitar Competition. As well as building guitars, Stephen does high quality restoration work and has worked on some of the finest guitars in the world including Antonio de Torres, Hauser, Fleta, Bouchet, Manuel Reyes, Ramirez, Fabricatore and countless others. he also teaches the art of guitar making for 2 months every year to students from all over the world.
Charles Hoffman Well respected maker and repairer who has been in the business since 1971. Lots of pics of guitars in progress.
Jack's Instrument Services Jack Ellis's guitar repair and setup workshop in Cheetham Hill, Manchester. Wide range of services and a great website - should give you lots of ideas
Kovacik Guitars Kovacik Guitars and Fretted Instrument Repair was founded in 1995 by luthier Steven Kovacik, who has been building and repairing guitars since 1986. Steve is a specialist in building and repairing flat top acoustic guitars, and is a CF Martin Authorized Warranty Repair Service agent. He's also worth contacting if you're looking for vintage tuners for a guitar as he as acquired a large stock over the years.
Manchester GuitarTech Steve Robinson's website. Steve is one of the North-West of England's leading luthiers, and his website is full of useful information.
Stefan Sobell I've never met him in person but feel I know him well as I've worked on many of his instruments and owned a few. Apart from his distinctive guitars, it's hard to imagine traditional music without his 'cittern family' instruments.
String Instrument Repairs Ian Robinson's workshop in Bognor Regis. Unlike most luthiers, Ian provides a full service for violin family instruments as well as anything with frets in.
Taran Guitars Rory Dowling has been building guitars, mandolins and bouzoukis in Fife since 2002. He combines traditional excellence with innovation to create a range of distinctive and sought-after instruments. As Martin Simpson says, "Rory is on track to be one of Britain’s most creative and successful guitar makers."
Russ Wootton Russ Wootton builds fine small-bodied acoustic guitars. I bought one in 1984 and used it for over 20 years. The inspiration is from the American tradition of steel-strung guitars but the construction process is that of the top classical and Spanish luthiers.

Green metallic Strat

Martin OM-42s

Daphne Blue Strat

Vintage 50s Tele