Definitely defrost it - in a cool room, not in the fridge and certainly not humming in central heating.

You might try brining it - boil up a load of water with lots of herbs and things like mushed-up juniper berries and peppercorns, plus some salt (kosher salt is best), then let the mixture cool and plonk the defrosted turkey in for five or six hours, then take it out, feck out the water, pat the bird dry and air-dry it in a fridge for another hour or so. Then cook it as normal. Makes it taste much tastier and moister.

+1 for using a meat thermometer - you can get accurate ones that sit in the bird in the oven and trail their cord outside to the end that reads the temperature.

If you want nice recipes for this, search the BBC.co.uk website.