I meant to buy an ericaceous compost in the garden centre because I need to plant some heathers, but I couldn’t see any. Could I use “Multipurpose compost with added John Innes?” It says on the packet that it contains “a blend of loam, perlite, course grit, sphagnum moss peat and fertilisers.”
Check which kind you have. If they do not mind lime, use the multipurpose but mix it well with the soil. If they need acid soil, get some ericaceous compost, the other can be used for other plants.