See https://www.gov.uk/smoking-at-work-the-law
Essentially it is permitted to smoke in company vehicle if it is for the sole use of that driver. A company is within it rights to ban smoking in all of its vehicles. If these are vehicles are solely for the use of the named driver than it’s up to you. Basically you have to decide who sets the policy you or the fleet manager.

Benefit in kind is not relevant-still company vehicle, you still set the policy.

I would say save your energy for more important battles.

I can't see why the signage in cars is needed as long as the company-wide ban is clear.

Sorry but I am still not convinced that if our policy states that vehicle are no smoking that this is sufficient and we do not have to display signage in vehicles.
The Smoke-free (Signs) Regulations 2012:
Duty to display no-smoking signs in vehicles
2. Any person with management responsibilities for a smoke-free vehicle shall be under a duty
corresponding to that mentioned in section 6(1) of the Act to ensure that at least one legible no smoking sign is displayed in that vehicle.

I agree that having the company logo plastered all over the car makes it obvious that its a company car and is far more likely to attract a prosecution.
However, a company car is still a company car even if it does not have logo's, etc...
Therefore the requirement for signage (no smoking in this vehicle) should still apply.
Shouldn't it??

As mentioned previously if someone is the sole user of that car for company business then that vehicle would be exempt from the reg's and would not require a no smoking sign.

If your company has decided that all vehicles are no smoking regardless then that's your choice but legally the vehicle would still be exempt.

But if you want to put signs in the cars and your company pays for the cars, put signs in the cars.

For goodness sake.
Who cares if it has a NS notice in it or not.
Not H&S legislation - enforced by EHOs as public health law - how will they know if it's a company car if it has no logo? They have to catch you first.
It's not 'our' battle.

Even if the company vehicle is signed should you encounter one of these extremely rare Environmental Health Officers they do not have powers to stop a vehicle, only issue the fine (understand this is given as the reason for no "prosecutions" under the October 2015 ban on smoking in vehicles carrying children - a much more visible offence than a relativley small sticker).

"2. Any person with management responsibilities for a smoke-free vehicle shall be under a duty
corresponding to that mentioned in section 6(1) of the Act to ensure that at least one legible no smoking sign is displayed in that vehicle."

There is more to this than meets the eye, as there is nowhere in The Smoke-free (signs) Regulations 2012 that defines what a "smoke-free" vehicle actually is. Instead, one is directed to the The Health Act 2006 Section 5.

This states (among other things):

5 VEHICLES
(1)The appropriate national authority may make regulations providing for vehicles to be smoke-free.

(2)The regulations may in particular make provision—
(a)for the descriptions of vehicle which are to be smoke-free,
(b)for the circumstances in which they are to be smoke-free,
(c)for them to be smoke-free only in specified areas, or except in specified areas,
(d)for exemptions.

But there is still no reference to any specific regulation by a "national authority" as to any provisions made under section 5 (2) above, to actually define what makes a vehicle "smoke-free" and by virtue of this, obliged to have a sign.

No wonder people are confused! HOWEVER - it HAS been defined...

This is on the www.gov.uk/smoking-at-work-the-law

SMOKING IN WORK VEHICLES
Smoking isn’t allowed in any work vehicle that more than one person uses, eg:
taxis
buses
vans
goods vehicles used by more than one driver
company cars used by more than one employee
A worker can smoke in a company car that only they use if their employer agrees.

A whole lot clearer methinks.