Hi my name is Brian, there are unfortunately no serviceable parts on these things. you will probably have to contact Worcester to get just the clock as everywhere else I know only sells the complete kit. the part number you require is 8-716-106-191-0
here is the pdf link to the manual for you and that part number is on page 11. On page 6 it tells you how to marry transmiter and reciever. but I am sure whoever you purchase the unit from will explain in full detail what you need to do.
Oops sorry i will try again
http://www.worcester-bosch.co.uk/cache/file/431/mt10rf-user-instructions--mk-ii-models-from-aug-09.pdf Ok i have had to use a different manual the part number is on page 16 of this one and the radio link is on page 10
No sorry I am pretty sure they are not compatible with other units,