No shed and not eating

Hi. Well I've commented before about how my snake sheds on the 18th of every month give or take a few days. Well he completely missed Decembers shed. People are sayin it maybe due to it being winter.
He looks dull in colour like he's goin to shed soon. I've put a moss hide in the viv and daily baths.
Today he's due to feed but he's just not bothered he goes near the mouse but then leaves it. He's never refused a feed since I've had him.
I bought him as a hatchling. In February I've had him 1year. He's currently 137g so has gained 5g in a week

What are the temps, and how are you regulating and measuring them?
Personally I don't think you should be needing to bathe him daily. That is only necessary if there is stuck shed, I believe. Because corns are from North America, the humidity is normally just fine the way it is - although with the dry Winter air a moss hide, which you've provided, should be plenty!
With those daily baths you could also be stressing out your snake, so I'd definitely advise to stop that ASAP.

Have you changed anything lately, such as the set-up, a new hide perhaps, or anything else in/around the vive?

It could very will be a simple fix

The temperatures are all fine. 28c at his fave spot. He has just a heat mat and a bulb to top up the heat as it's too cold with just the mat. The only change he's had is that I've moved him from his faun to his 4ft viv but he's been in it since just before Xmas

"All fine" really isn't specific enough. Ambient should be 70-75F (21-23.8C) and warm spot should hover at 85F (29.5C). If the air is comfortable for you, it is comfortable for your corn and a heat bulb is most definitely not necessary, especially with a UTH.

I really advise a thermostat to maintain the heat source, as UTHs without can skyrocket to over 120f! (48.8f)

Once all those things are taken care of and you've stopped bathing him and leave him be for awhile, things should go back to normal. It could just be that with the holidays, people are busy and there's more noise and activity around.

More often than not, changes in a snake's behaviour are due to their environment. Little changes can go a very long way.

Best of luck!

P.S.
I hope you are measuring with some kind of digital thermometer, probe, or hand-held thermostat and NOT dials or stickers (as you didn't say which you were using)... those are not appropriate tools to measure temperature.

The heat is measured by a digital thermometer with probe. I check it regular. With the light and the bulb is is anything from 28-30celcius.
Slight drop during the night to around 26c.