Not sure if you are still looking for help on this, but here goes anyway.
Firstly, you can download manuals for this boiler from the C&M website -
www.chaffoteaux.co.uk
If you download the Installation and Operating Instructions manual, it has a table of the fault codes on page 15. Also found on page 10 of the Maintenance and Service guide.
In your case, 70 & 80 flashing means no flame detection.
I would assume this is referring to ionization electrode, which detects that the burner is lit. Try cleaning it (it's metal and can become oxidised). Otherwise, try replacing it.
I have fault 40+60+80, which appears to be a common fault with these boilers. This seems to relate to a faulty relay on the pcb, which drives the flue fan.
Replacement pcb is over £130, so I am attempting to replace the relay myself, though struggling to find a supplier of the correct type of relay.
Which, by the way, is what brought me here today!
Graham, September 2008
