I haven’t heard of anyone who has any of these signs, but you might be able to use data from the Big Hedgehog Map https://bighedgehogmap.org/ as evidence. That may depend on whether any fatalities/live hedgehogs in the area in question have been reported to it.
I spoke to someone in my local council (before these new signs were announced, but I imagine there will be similar requirements) and he suggested finding a suitable location, where there weren’t too many other road signs (I believe the trend is towards reducing unnecessary signage), where it was safe, i.e. possibly not on a bend, etc. basically a suitable location. But you might want to stress the danger to other road users (such as cyclists) of hedgehogs dead or alive being on the roads, which may be considered to be as important as the hedgehogs. But really, do the leg work so that the council’s work is minimal (important in these days of cuts to local authorities).
At the time of the conversation, it was a question of a possibility of a temporary sign and I didn’t think there was a suitable site for that sort of sign, so didn’t pursue it. Also road fatalities of hogs were low so it seemed the area wouldn’t be considered a priority.
Good luck. Let us know how you get on.