Ah, I see Toby....
MAke sure the tiles are clean firmly fixed and grease free. Then score them using a tile scorer to give them a 'key'. Then PVA them 3 parts water to 1 part PVA. Let dry. Then use a good sticky adhesive. Before you grout, you are supposed to let the adhesive dry for a day or so - but its up to you.
Dont run any beading across the top of the tiles - it will look daft. Just grout them up nicely. And try to tile from the worktop upwards to the bottom of the cupboards so that the extra 6mm protrusion is hidden under the cupboard. You will then not know the difference if they have 1 layer or 2 layers of tiles.
Hope this helps
Anthony