Hi Gemma
my suggestion would be to over-winter but others may feel this is too cautious.
I like the Tortoise Trust Safer Hibernation Guide
http://www.tortoisetrust.org/article...bernation.html
and the Tortoise House guide is also well respected
http://www.thetortoisehouse.com/
The tortoise trust guide will say you should over-winter if your JR is right. I think it's worth checking your measurements.
My own experience with keeping them up is that a lot of heat and light is necessary to keep them up if the slowing down process has gone past a certain point. After the tortoise is back up to normal speed (as it were) it will then seek out heat and light just like it has all summer.
If I was in your position I would get this tortoise up and make sure it is exposed to a lot of heat and light which is likely to work given your tortoise hasn't hibernated previously. But as you know hibernation is one of the topics that there is lots of strong views about and I'd urge you to get some different opinions and make up your own mind based on your experience of keeping this specific tortoise, what his current weight and length are, what kind of summer he's had (e.g. did his weight go up and was he eating well and having decent weather).