There is precious little documented about Boosey and Hawkes - so open to suggestion ( and correction ) ...if anyone knows more!
After their well known Professor and Concert, they seemed to have started importing Czech basses made by Artia, rebranded and labelled ‘Excelsior by B + H’ . This carried on through the 1960s up till the 1980s. They came from the ‘Cremona’ factory in Luby and were hybrid. This factory is now where Strunal manufacture their instruments as Europe's largest manufacturer
http://www.strunal.cz/en/default.aspx
B + H brought out the Golden Strad during this period I understand made in Hungary in the 1960s/ 1970s. And there was also the 400 range - not established a date for the manufacturing window but I do know that its a laminate top, back and sides and Czech made in around the 1980s. By 1992 it seems that manufacturing went to China. The 400s go for anywhere between £750 - £1000 as do the Excelsior and Golden Strads. They are a good quality instrument and seem to be robust.
I have started a Facebook page for modern B + H so if anyone has info or wants to post there ...then heres the link!
http://www.facebook.com/pages/Boosey...28245287344781
...or is that exceedingly bad manners to direct people to another web site !!? Ken, delete if this is bad netiquette!!