If your tortoise is still hibernating you should get him up NOW and keep him indoors under a heat lamp until the weather warms up. It is very easy – you just need a pen of some sort and a 100w spotlight which you can suspend 30cm above the tortoise as a basking light, with background heating in the room as well.
Give him a good soak in warm water every day to rehydrate him after the prolonged hibernation. He should be active and eating within 24-48 hours. If not, he may not be warm enough.
If you are concerned please call one of our surgeries to speak to one of our vets, and if he is not eating within a week you should seek veterinary advice.
Further details can be seen at the Tortoise Trust website