At work i normally drive the same truck, unless my truck has been taken off the road for whatever reason. I had to use a truck a while ago which is quite old & had no heating wotsoever, I didnt mind it then as it wasnt that cold & it was for 1 day.
However my truck was taken of the road middle of last week & once again ive been given the truck with no heating. Neither the night heater or the normal heater work. Not only does it get bloody cold at times but it tends to mist up quite easily when it rains. I know i dont do nights out but even so can they make me drive it?
No they can’t make you drive it, they aren’t holding a gun to your head so you can just say no. Of course they may decide they no longer want to employ you. 
Then it comes down to whether it is a safety thing having no facility to demist the windscreen.
Not being able to see out of the windscreen,is an offence,and having no way of demisting it,makes the vehicle unroadworthy in my opinion.
There is also a health and safety issue here.
If you were to work in an office,the heating would have to be at 16 degC,the fact that your truck is,in effect,your office,means that you would be entitled to have some way of heating it,and as the heater doesn’t work,then you could,in theory refuse to drive it.
Ask your boss if he would be prepared to drive it,given it’s current condition,and see what his reply is.
Just my 2p’s worth.
Ken.
I don’t ask for a lot especialy if I’m on day work, but a shed to far in my opinion.
I have a similar problem with a couple of the buses at our place, when I questioned it (they sent the bus down to do a swap) I was told “I don’t care about the heating, Iwe need the other one for schools!!!”
This is one reason why I am seriously thinking about not going back after my hols. (this bus has been repeatedly defected for this fault for about 2 months now.
When I do leave, I think I shall be having a chat with vosa and the HSE about this particular firms antics
Ah cold buses, reminds of one particular incident that took place when I worked for a smallish firm in Sheffield.
I was driving a freezing cold (But powerful and fast) Leyland National MK 2, it was that cold we nicknamed it the flying fridge!
I had it one day and stood it for about 2 hours where I realised both my feet were going numb and my hands had turned blue. I phoned the yard to be told you’ll have to carry on, no spare buses, to which I replied well in that case I’ll sit here then till one becomes available. I sat there all afternoon waiting!
They couldn’t sack me though for refusing to drive it, I was working my notice!
The bus companies tend not to bother with trivial things such as heating, means they have to spend cash getting them seen to, and we can’t have that can we…