I have a digistat scr with a flashing red light and no heating there is nothing wrong with the batteries, this only occured after a poweer cut.

Try this first before condeming the unit.

1. Turn off the power supply to the Digistat SCR (receiver unit)
and leave for 5 seconds.
2. Turn on power to SCR unit and check red light is on.
3. Press override button No.2 and check the green light comes
on and boiler fires.
4. Press & hold down button No.1 (Keep depressed), then
press No.2 and keep depressed. {The Red LED light will flash
a couple of times and then it will go out}
5. Now release both the buttons – {the two LED lights should
come back on}
6. Get the Digistat+2RF/+3RF unit and stand two metres away
from the SCR unit with the Digistat+2RF/+3RF unit in your hand.
7. Remove the battery cover and fit the batteries.
8. The Red LED light on the SCR will now flash for approx. 7
seconds.
9. This confirms that the radio signal is being sent and
received.
10. The Digistat+2RF/+3RF and the SCR are now successfully
linked by a dedicated RF address.