I had to look up Ericaceous mix and this came up. Looks like your seller is advicing a mix with acidic soil

• Ericaceae, the heather family
• Calcifuges, all plants which dislike alkaline (chalky) soil - including heathers, rhododendron and camellia
• Ericaceous bed, a bed with acidic soil typically having a pH between 4.5 and 6 used for growing Calcifuges
• Ericaceous compost, a commercial formulation of growing medium designed specifically for ericaceous plants in containers

Thanks for replying yes he did say that but I would like to give it the "best" medium to grow in. whats the difference between citrus mix and the ericaceous mix? if anything im thinking of just getting some ericaceous compost and mixing it with everything I have which is John Innes no3,coco coir, clay pebbles, rockdust, vermiculite, perlite and bark chippings or should I get the citrus mix :s