When I last saw my GP about chronic lower back pai he said it was up to me really, he couldn't see what a specialist would do. He offered physio, but left the decision to me. I opted to see the consultant and it turns out I need a new hip!
If the GP can't sort it, then I generally push for a referral.
Last time I needed a specialist, I had to be quite forceful with the GP.
I was dizzy for weeks after any plane or boat journey and he said it was "viral labythrinitis (sp?)" which I immediately knew was a crock of shit, because it would have been far too much of a coincidence that it happened after travelling.
I basically told him it was a crock of shit, and he referred me. And I got the correct diagnosis of Disembarkment Syndrome which was what Dr Google I had thought all along.