Would appreciate any advice where I might buy following type of thermostat. Tolerant of atmosphere in a greenhouse, although would be protectively housed so rugged, domestic variety acceptable; preferably low-voltage (either battery or transformer); digital display covering ambient temperature and setting points; battery back-up of set programmes; two low-voltage outputs to secondary relays, minimum setting to control heating, maximum setting to control cooling fan. Optional hysteresis would be ideal, however, adding this probably suggests I still believe in Santa Claus.
Velleman offer a DIY kit with similar specifications, but in my experience this is alarmingly unstable in operation and if the mains blinks loses all its settings, cheerfully displaying the message, 'FAIL'. At 0300hr on a winter's morning this is unhelpful.