Here's a little more I was able to find. I noticed they also did one or two of Donovan's. This was from a jazz site:

Castle Communications
(South and South East)
Lee Simmonds, Castle Communications plc, 29 Barwell Business park, Letherhead Road, Chessington KT9 2NY.

020 8974 1021 (office tel)
020 8974 2608 (office fax)
Activity: Production/Re-Issue
Record last updated on 02/03/98
Catalogue includes Pulse - mainly Blues, Country & Folk with a scattering of Dance Band & Trad, KAZ boxed CD sets - Duke Ellington's private collection, Classical Big Bands, Black Box (4 CD's including tracks by Mingus, Monk, Charlie Parker, Brubeck), White Box CD set (out Apr '98). Recordings by Abdulla Ibrahim, African Jazz Pioneers. Re-issues of Traditional jazz. Have also just bought the Concord jazz label (USA) with a catalogue of over 600 CD's.