Yup, sorry - found it:
http://www.wickes.co.uk/Granular-Sub-Base/invt/224664
OK, so for a 2.4m paving circle, with a 3:1 mix, the paving expert calculator recommends:
42 kg cement
152 kg sharp sand
228kg gravel (mot presumably)
Am I right in thinking that all the Wickes 'major' bags...