The winters here in Crete are cool, but not freezing like the UK winter. The coldest it gets is a low of approx 6-8 degrees centigrade, this is chilly. Considering that you probably will be living in a concrete house with ceramic tiles, which holds the heat or cold and makes the chill factor even worse. Therefore you will need some form of heating for your house.
This is probably the best solution all round. If you are buying or building your house, take the option of central heating seriously, do not assume Crete is always warm.
Air Conditioning in Crete is another good solution as it will enable you to cool your house in the summer, aswell provide heating in the winter. You need to ensure that the air conditioning system installed is of sufficient capacity to heat or cool your house, taking into account the cost of electric as opposed to oil for a central system.
If you want to rent a house in Crete then your choices become a little more difficult, rent tends to be higher with central heating or air conditioning. Many houses for rent will have no heating system at all, if you ask the landlord to install either system, you will probably end up paying for it in your rental charge. There are other alternatives to consider, gas fires, fan and halogen heaters, these are not really for heating a house, but for close comfort.
Wood burning heaters are popular in Crete and there are many shops where you can buy these heaters. They are are very effective and quickly produce warmth through out the house. The tricky bit is getting a hole through a wall and setting up your chimmey. The rest is back to the middle ages, humping wood and lighting fires.