The service that has existed pre-2015 has had up to 4 providers and all of them had major short-comings. There were reduced numbers of aircraft in some flights, poor aircraft availability, poor contract specification, absence or late introduction of critical role equipment, resources diverted to war-fighting, poor and unco-ordinated reporting, no de-icing, poor communications, and late introduction of a unified tasking regime
Well that is certainly a set of sweeping generalisations Jim.
Granted the Sea King had its problems with serviceability on occasions during the last 30 years but lets see what the new shiny aircraft do when all their flights are up and running and coping with 2 - 300 jobs a year.
You conveniently forget that until a few years ago, the Mil SAR Flights held a full second standby, aircraft and crew, at RS 60 - will we ever see that capability in this contract? Not a chance. Yes, sometimes its availability was limited by aircraft serviceability but the stats will show a very high percentage in its favour.
I don't know which resources you think were 'diverted' to war-fighting but it wasn't aircraft or crews since any deployments of personnel were managed without compromising UKSAR.
If by poor comms you mean HF - that is valid but we seem to have got the job done with it and it is unlikely that the new contract would have Airwave had it not been used and proven extensively on milsar.
Presumably by poor contract specification you are talking purely about civsar - perhaps the introduction of the 139 when it had inadequate lighting and no cleared overwater SAR modes, yet was declared ready for 24-hour ops.
As for absence or late introduction of critical role equipment - do please clarify.