Vokera HE35 has no heating but have hot water, how can I fix this?

Our boiler is not working properly on return from holiday we found we can only get hit water & no heating.
I've checked the water pressure, I've turned it off & back on. No results. The digital wireless thermostat seems not to be sending the signal, & I changed the batteries & reset it & no result.
In not sure if its a problem with the boiler or the thermostat.
The light on the boiler is flashing green.
Any ideas??
Thanks in advance