Where I do have a grudge is when a pilot talks about an issue with a service, and then someone on this forum sits on their hands and replies with a tone as if to imply "GA does not pay anything and therefore deserves nothing"
The NATS people have pointed out your errors regarding who is responsible for your other grievances (ie. not NATS), but as an ATCO at a regional airport, I thought I'd take a crack at this bit.
In the OP's situation, in all likelihood the controllers at the non-LARS regional airport are employed, either directly by the airport or by a contractor, to provide services to aircraft inbound to or outbound from that airport, and to aircraft wishing to transit the airspace associated with the airport. Nothing else. If you are passing nearby, you may be lucky and get a great service, or you may be unlucky.
The point is, anything you get from a non-LARS unit has to be regarded as a freebie and taken with the knowledge that you are at the very bottom of that unit's list of priorities. It's not that the controllers don't want to give you a seamless ATSOCAS experience - in the main we take professional pride in doing our best for everyone. But, these days more than ever, some of our employers are very clear indeed that freebies to non-paying customers are not what they want us concentrating on.
That's the way it is, this is what informs the responses that the OP had to his question. The joined-up radar service that you want could exist in this country if there was a massive reordering and nationalisation of the ATC infrastructure, and a way to pay for it all could be devised, but that's a matter you should be taking up with the government and the CAA.