I presume you are talking about the Firebird SuperQ boiler. They have a built in timeclock that can separate HW from CH, however, only if they are wired to a motorized valve on the CH plumbing circuit. Most of the ones that I have come across are not installed this way and the timeclock can only be used as an on/off timeclock, heating both HW and CH simultaneously.
If you have got a motorized valve, then it is pretty straight forward to bypass the built-in timeclock on the SuperQ. The motorized valve takes the live from the new timeclock, when the valve is fully open, the Auxillary becomes live which is then wired back to the boiler and circulating pump. You can install a two channel timeclock, the ones we use are the Horstmann H27XL. It is very user friendly and has features such as Boost and Advance to override the system outside of the timed programmes. Just wire the live through the new timeclock to the motorized valve and then the auxillary from the valve to the boiler which becomes the switched live to the burner/circulating pump.
If you do not have a motorized valve on your heating, then a single channel 7 day timeclock will suffice. This will now become the switched live but you will not be able to separate HW from the CH. Alternatively, install a motorized valve on the CH circuit and then you can heat HW without heating CH.