A belated Merry Christmas!

Please can anyone identify a source and part number for the plastic mixer
valve from inside a kitchen hot/cold water mixer tap -- see photographs
at the links below:

http://www.chapmip.demon.co.uk/Temp/PC280106.JPG (170 KB image)

http://www.chapmip.demon.co.uk/Temp/PC280107.JPG (160 KB image)

I'm hoping that it's possible to purchase this part independently of the
entire mixer assembly because it has definitely failed (close examination
reveals a broken plastic lug that causes the tap to be jammed in the "on"
state) and it is easily replaced from the top, whereas changing the whole
assembly is a much more complicated (and presumably expensive) job.

I don't recognise the "K" logo and there isn't an obvious part number on
it, assuming that "19-01-99" is the date of production.

Many thanks in advance for any pointers.

Happy New Year to all.
--
Ian Chapman