Hi - sorry not been on - there is a large Safeways or Morrisons outside the town (Saltcoats ) at roundabout (and a MacDonalds too ) see google map
maps.google.co.uk/maps?hl=en&safe=off&q=saltcoats&ie=UTF8&split=0&t=h&ll=55.639043,-4.750128&spn=0.0 33523,0.047379&z=14
if you zoom out from this you'll see the beachy bit where the caravans are behind - separated by the railway line.Erm, the google map jumps a bit, basically shop is at the roundabout end of Kilwinning road - white roofs, just move map to right a bit.
In town there was also a smaller supermarket - can't remember which one though, sorry.