Davo
In principal you would not be committing an offence. Unless as Civvy states the extinguishers are required by virtue of an enforcement notice. If the fire authority believes you need extingishers back in place it may issue an enforcement notice asking you to do so. If you dont successfully appeal the requirements of the notice or just ignore it, you would be commiting an offence.
A few things to be careful of here...
Firstly if your RA has determined they are required, then really they should be provided, thats the whole idea of the risk assessment process. That's not to say an assessment shouldn't be reviewed or questioned, but the danger is the organisation may decide the findings of the assessment are a little inconvenient, and choose to ignore the bits it doesn't like. Clearly that is bad practice, to put it mildly!
Here are a few things to I would consider:-
The first priority would be to establish if you have more fire extinguishers than you actually need. Can they be reduced? Are they over specced? Are they in the right locations?
Secondly consider the knock on effect of not having extinguishers. Could it be of detriment to operational resillience, or continuity, could it mean ultimately a fire could cause more damage to your assets? Maybe it would, maybe it wouldn't.
Thirdly what about areas such as your custody suites? Many were designed with excessive dead end conditions, single direction of escape with perhaps secondary access to a secure outside yard from which there is no onward escape.
You need to consider if a fire started in the custody suite cell area, could the custody sergeant and their team be able to secure, and evacuate those in people in custody before the MOE is compromised? In my experience the cells are normally fire resisting boxes, smoking is not permitted any longer, and a fire in one cell should be contained.
But are those measures maintained in a effective state? Is that FR in place? Will a fire be contained?
Fourtly HMG is looking to make cuts in the fire service. They want less fire stations and fire crews, the idea is to push for business to mitigate the effects of fire so that we don't need so many big red fire engines whizzing around everywhere. So I get the impression that mitigating the effects of fire will become a very hot topic in future , and furthermore the penalties for not mitigating the effects of fire will become more and more severe.