B&H is little-known in the US apart from the fact that they once acquired Buffet-Crampon. It was not a happy marriage. B&H is known more here in the USA for its fine brass instruments made in the British Brass Band tradition. Still, they made their own "English Bore" clarinets up until the Buffet acquisition, and they are preferred to this day by many clarinetists throughout the Commonwealth. The pinnacle of the B&H clarinet family is the 1010, also known as the "Symphony". They feature .600" bores, and when encountered for sale are often found in a B-flat and A matched set. Other Boosey models are configured with a bore that "only" measures .593"(!).
B&H clarinets are well-known for high-quality wood that's unusually resistant to cracking.
The gotcha with Booseys is some Regents made just after WWII were built with Mazak keywork that's prone to breakage and near-impossible to repair. I've also come across a hard rubber Edgware that had porous, flimsy brass keywork with really shoddy nickel plating. The vast majority of B&H's have sturdy, forged nickel-silver keywork. Just as with Pruefer and other mostly-forgotten brands, the ones with decent keywork cost no more to buy than the pot-metal abominations--so don't settle for one with crummy keys. It's possible to find old Booseys with excellent wood bodies and trashed keywork.
The restorer of my 8-10 advises that keywork is mostly interchangable between all the .593-bore models, and that the bore dimensions and tone hole placement are also identical--no matter if the body is made out of wood, hard rubber, or plastic. The hard rubber Booseys are said to play exactly like the wooden-bodied models.
Boosey models included:
STUDENT: Regent (wood); 1-10 (plastic)
INTERMEDIATE: Edgware (hard rubber); Edgware (wood); 2-20; 4-20, Stratford, Emperor
PRO, .593 bore: 8-10, Imperial, 926
PRO, .600 Bore: 1010; 10-10; Symphony. Note that the .600 bore instruments require a B&H or Peter Eaton mouthpiece made specifically for .600 bore.
There were some stencils sold under the B&H label. The model 78 was a Bundy 1400, while the 400 was made by Amati.
Some sources on the web maintain that the Emperor model survived the Buffet acquisition and lived on as the Buffet E13 International.
Counterfeit Boosey & Hawkes clarinets have been made in India. They're labeled "Bessons" and are all Albert system. They do turn up on eBay now and then.
The B&H clarinets represent the most accessible way to sample the English clarinet tradition. The .593-bore instruments really aren't THAT different from a big-bore Selmer, like a Centered Tone, and can be a very affordable alternative.