As the ceramic floor tiles were fairly expensive I decided not to tile
the complete kitchen floor but just to tile up to the front legs of the
base units, locating the plinth on top of the tiles.

I have now realised that the concrete floor varies in level by 7mm over
the 4 metre length of a row of base units which means that I will have
to either

i) level the floor or try to adjust the level with varying thickness of
tile adhesive

ii) scribe and cut the lower edge of the plinth to match the varying
height of the tiled floor

iii) fit the base units and plinth and tile up to the face of the
plinths.

i) seems to be a lot of hard work or a lot of adhesive/self levelling
compound, ii) a bit fiddly, iii) may make it awkward to remove the
plinths at some time in the future in the unlikely* event that I need to
gain access.
* I am cutting access holes in the back panels wherever there may be a
need to get to service valves and power outlets.

Grateful for your thoughts.
--
Robert