The hallmarks on your brooch are for Edinburgh, 1971. Therefore the millefiori cane will have been one made by Paul Ysart.
However, strictly speaking, we should refer to the Brooch, as a whole, as being "Caithness Jewellery, designed by Colin Terris and containing an Ysart millefiori cane".
Further infomation can be found in Frank's ysartglass pages:http://www.ysartglass.com/PaulYsart/PYP5over.htm
and also in Colin Terris's own site at:http://glasswatch.mysite.wanadoo-members.co.uk/
Frank (as well as others), while I am here, it may be worth noting that the ysartgalss info gives:
Colin Terris designed a range of brooches and pendants inspired by traditional Scottish design and hired Lucia Polanski as a jewellery designer; she produced the rings, earrings and cufflinks designs.
But Colin's pages say:
Lucia joined Caithness in 1970, and designed a Ring Collection which was very popular. Colin Terris concentrated on designing Pendants, Brooches, and Cufflinks.
Is there some confusion here, or is it the case that both Colin and Lucia both produced Cufflink designs?