Support Plan - How do you know?

In February, after getting a copy of the letter to my GP confirming the Autism Diagnosis I immediately made an appointment with the GP to discuss things.

The appointment was frustratingly unhelpful. It was basically 'try talking therapies' who locally don't cater to post-diagnosis or autism support in general. The doctor in question also didn't have much of an idea of what support groups or other things would be available.

As I think about it now, I'm wondering how would I know if that GP actually put a support plan in place?

I've not received any letters or other formal information regarding a requested support plan. Does this likely mean that I don't have one? Would any of you recommend that I send the form letter [https://www.autism.org.uk/advice-and-guidance/topics/diagnosis/after-diagnosis/formal-support-following-an-autism-diagnosis] and make the request 'more official' than the in person question at the appointment back in February?

My instinct usually is just to tough through things, to just live with things, but I do have to admit that I find contacting and making doctors appointments a bigger thing than perhaps I should. It all feels like a lot. I have a sensitivity when it comes to needles or getting bloods drawn, so perhaps might be useful to have stuff noted? I'm also dealing with some ongoing pain and joint issues (into years of dealing with that now). Would a support plan factor this stuff in, or...

Basically:

1 - Is a support plan necessary?

2 - How do you know if one exists with your GP?

Thanks in advance folks