Thanks sospan, no it wasn't cheap but we went through a reputable local supplier so I expect they'll be helpful if we have to go back to them. The kitchen fitter left the sealed edge of the plinth at the bottom to avoid moisture getting into the chipboard, so the top edge is where he cut it down to fit. There seem to be different opinions on here as to whether that's the right way around. I don't really mind as long as I get a nice well fitted finish and the board is protected from water damage one way or another.
Even the standard finish edge will perish in time because of the floor being mopped and the water getting in. There are two easier options; fit an edge protector channel on the bottom of the plinth or get the kitchen fitter back to run a bead of sealant along the edge. What I do as well is to put something like this under the cupboards. Some brands stay active for several years http://www.pestcontrolsupplies.co.u...-powder-300g?gclid=CJChhMiAyMoCFasEwwodEREAiQ Not saying you have them but it is a good preventative measure just in case we get a good summer and the little critters come in.
I've done the same for many years, a dusting of pest powder under kitchen cabinets, sink unit, bath, & vanity unit & shower tray.