Chopjock - they are always available during the hours they are allowed to operate and if called will respond - BUT, if the weather is outside limits it is outside limits and they won't go (unlike, it would appear, some US HEMS operators).
Being useful to the emergency services doesn't mean launching in all weathers - even on SAR we have have the option to say no if the weather is too bad to achieve the aim. We might try a bit harder to get to the scene but it is because we have a fully IFR capable aircraft and a 4 man crew (with 2 pilots) to spread workload between - AA and police are single pilot.
I don't know how many times you have to hear from people who do this stuff professionally that Mr Paxman's idea is fraught with danger but he really doesn't have a clue about what he is trying to do.
As TC points out, JP has a big wallet and a bigger ego and should keep well away from playing at emergency services. If he really wants to do it then he should get an ATPLH and some twin time and apply for a HEMS or police job.
I am very disappointed by the editorial - is the editorial team really so unaware of the potential issues with JP's plan?