Unless you have a very very severe sinus there shouldn't be a need to see a specialist? General surgeons are trained to deal with them, I saw a plastic surgeon who did a skin graft which sped up healing. Each surgeon probably has their own methods which they've developed over time so it might be worth just getting consultations with different surgeons to get different opinions.
I think if I was to put myself through surgery again I just feel I would mentally feel better if I had a second opinion. My surgeon is good apparently and is a colorectal surgeon and my Gp said I should trust him and no to go private for a consultation but I'm not sure what to do.