Having researched further, looking at old catalogues, it seems it's a WHS Halo System 10 (pre Veka's ownership of Halo and development of System 10 - Veka System 10 uses a different bead).
https://web.archive.org/web/20061231103354/http://www.whs-halo.co.uk/files/sys10brochure.pdf
Appreciate...