I've done the kitchen with the Volex black nickel flat stuff.
Looks very smart, but the lugs on the box need to be at least 1/4" below
the surface of the tiles / wall. The plastic gubbins of the accessory is
riveted to the metal front plate through the fixing holes. Generally not
to much of a problem if boxes were flush with the plaster, which has
then been tiled on top of.
But then the screws can be too short if the box is really deep, and
they're colour matched screws.
On a plastered only wall, I think it would be wise to sink the boxes
2-3mm below flush.
--
steve

Cheers for that Steve, so by the sounds of this I would get away with
fitting them on the tiled areas of the kitchen but with regards to the
rest it would seem a lot of hassle sinking the boxes deeper in,
especially with so many sockets and switches to replace, what do you
reckon.

Just go with the other Volex ones as opposed to the flat plate ones