My recollection of the Wales fixed wing [and I have little doubt that it will be covering substantially more than that] is that in 'Plan A' of the launch 2 years ago it did not exist, Dyfed lost the [non-standard A109 airframe] without replacement and S&EW came off the [non-standard] lease arrangement to be replaced by one of the displaced airframes from England.
Meanwhile the temporary contract for Ollie Dismore had expired and he went off to Oxford for a while [therefore hands off the tiller] and the Dyfed fixed wing was created as a solution by the remaining team members faced with an intrasigent Dyfed Powys.
I have little doubt that matters like local weather, IFR etc were way above their pay grade. The result was that the Wales fixed wing solution [Plan B] was to be housed at a small airfield in the extreme of west Wales near Haverfordwest. 'Small airfield' is mainly allowing for the option to get airborne quickly without the need for runway queus.
The rest comes back to the basics of police and IFR. Most practitioners still stick to the assumption that if you cannot see it with your eyes its not worth undertaking the police mission. IFR is a 'get you home' safety capability in case of flying into IMC rather than an operational need.
The favoured fixed wing [wherever it is actually based] is a Tecnam and I believe that is not IFR anyway.