fault with my worcester 240?

If you turn the controls to water only and turn on the hot tap does the boiler respond?
If yes, its not likely to be the diverter valve.
If there is no response then it probably is.
Diverter valves can usually be repaired. There are several repair kits available, some with just a diaphragm and others with a full set of pins,seals and clips to fully re-condition the valve.

Depending on where you live in the U.K. and the type of kit used you can expect to pay from £60 to £100 for a repair or from £120 to £180 for a new valve fitted and working.
There are some cheap copy valves on the market which are o.k if you are planning to change the boiler in say 3/5 years which is why there is approx £60 difference in the price.
You may pay more if you are in larger city.
It's not really a diy job for most people and can produce one or two problems if you're not familiar with draining and refilling combi's.. good luck

T.h.s
June 2007