Have you asked in a tile shop ? Have you asked the original supplier of
your previous tiles ?

A relative of mine was in a similar position recently and some 2 - 3
years after purchasing tiles for a hallway they extended their kitchen
and went back to the tile shop. Matching tiles on display.

If you prefer not to go down this road have you tried a google search ?
Lots of links on there, eg. http://www.centraltilestudio.co.uk/

KG