Hi Michael, Hi Steve thanks for your help,
The effect I was looking for was a blistered surface similar to the image bellow where the curved top surface meets the edge surfaces on the same plane all round.

The surface in the image was achieved using revolve rail to revolve a spline around the profile which works well on simpler profiles but on these buttons it doesn't meet the edge properly so is difficult to join properly.

May try trimming curved surface flat and attempt to join with a rad.

Thanks,
Doug