There's a fair bit of confusion over what actually constitutes a bracket clock. Purists say bracket clocks represent the earliest type of English spring-driven clock that sat on its own shelf (or wall 'bracket') and this is certainly true in principle although the term 'bracket clock' was not actually coined until much later in the early nineteenth century. Before that, they were simply referred to a 'spring clocks' to distinguish them from weight-driven longcase clocks. But the vast majority never had a bracket and just sat on a cabinet or table, or even a mantelpiece if they were small enough; nonetheless, they can still properly be described as bracket clocks.
It's difficult to define exactly when a free-standing clock should be called a bracket clock and the term is frequently used rather loosely, particularly if the owner is trying to enhance its description to generate a sale at a high price. It is partly, but not solely, to do with size but whilst even an experienced horologist may find it difficult to describe where the division line lies in inches, he will always be able to say which side of the line a particular clock falls when he sees it. Generally, the term 'bracket clock' could be applied to anything from the one with its original wall bracket mentioned above, to virtually any large or largish wooden cased spring-driven clock. For me, it tends to conjure up images of a 14 inch ebonised Georgian clock in Classical form chiming on eight bells with pull repeat, a brass dial with gilt spandrels and silvered chapter ring with Roman numerals, two subsidiary dials to control the timekeeping and silence the chime, triple fusées on chains, a crown wheel and verge escapement with chased and signed backplate and glass panels on all four sides. But as they start at around £5,000, they often remain images in my mind or on the pages of the excellent book on The Georgian Bracket Clock by Richard Barder which is a more affordable £45. Of course if price is no object, then take a look at what Sotheby's have to offer; you might be lucky enough to find a bracket clock by Graham, Knibb or even Tompion. It'd only cost what you'd expect to pay for a modest house in London so why not get one of each!
Unless it's pre-1875, a fusée or a verge escapement, my standard flat rate for overhauling a bracket clock is £125 for a timepiece, or £175 for a striker. For fusées, add £50 per train. If it chimes, too, expect to pay at least £300. These rates include stripping and cleaning, re-bushing up to two worn pivot holes, checks for wear and proper engagement of wheels, pinions and pallets, and correct set up to ensure it's in beat.
All paid for work's guaranteed for a year.