Danfoss make a great range, as to Heatmiser.
Google either for more info.
What I would get, in your case, is a "programmable thermostat". This is what the previous poster was describing. It allows you to set the desired temprature up to a few times a day, an well as setting it to a minimum (frost protection), or letting it come up for an hour a day.
You can also set it to holiday mode, which maintains a minimum temprature for the input number of days before going back to normal mode.
The programmable thermostat will replace the timer, as well as a thermostat, (if you have one).
I put one in my in-laws holiday home and it does the job perfectly.