How do I get an autism assessment?

Hi I'm 36 and recently had realisation through failed relationships and many other traits that I believe I'm autistic.

Yesterday I went to my GP and saw the actual Doctor and asked for a referral for an autism assessment and I explained why. 

The doctor clicked around on his computer for 15 mins whilst I'm sat Infront of him twiddling my thumbs and in the end he wrote a website down for me to visit and packed me off.

The website goes to a crisis team for mental health! I do not struggle with mental health, I do not have suicidal thoughts, or have depression or anything like that. I'm happy. I just think I'm autistic that's all.

The GP clearly had no idea how to refer me. 

Should the GP refer me or can I self refer for an assessment? 

I live in Kirklees district. 

Any help would be so much appreciated, thank you.