Hi - Self - Diagnosed and unsure what to do next...

Hi all

I am a 64 years old male. I have self - diagnosed as autistic  on the strength of some Youtube videos I watched recently. I have a previous diagnosis of ADD from about 25 years ago (private), this was refuted by Maudsley about 15 years ago because I don't apparently respond appropriately to methylphenidate... I tried the drug again a couple of years ago but it didn't end well.

My questions revolve around diagnosis and help.

Are there reputable online tests for autism that I could take to have a better picture of where I am with this.

I am based on the coast between Brighton and Eastbourne, could anyone recomend a therapist? I would dearly like to gain some sort of perspective on what to do about this 'diagnosis' - or if the diagnosis is inapropriate then some guidance generally.

Not looking for sympathy here just a grown up perspective.

Thanks in advance

Paul