Heating Digistat RF2 unit?

My ACL Drayton Digistat RF2 signals to the SCR receiver (which picks up the signal correctly) when I first insert the batteries, but after that it doesn't seem to send any more signals to the SCR unit - so then the SCR alarm light comes on and I have to turn the boiler on and off manually using the override buttons. Questions:
1. Is there anything I can do to fix the RF2 unit?
2. If not, is it still possible to buy a new RF2 and where?
3. If not, will the SCR work with a newer Digistat+ thermostat unit, and which?

Very grateful for any advice.