Frank - If you want to mix the leather with the vinyl, you will never get a perfect match - either for the colour or for the textured finish. In 1989, when I was re-doing my 1958 TR4A which originally came with red vinyl, I was told that the correct red was no longer available. I really wanted it to be the correct original colour. So the chap I was discussing this with (Jim Hawkins in Witney, west of Oxford, England) told me he could do it all in one correct colour - in leather. So I bought it all from him in leather and it's been there for 18 years and 100,000 miles. The only comment I ever got from a TRA judge in a concours event was the comment, "I've never seen such nice vinyl like this before". I caught him rubbing his finger across the surface. I told him judges are not permitted to touch the car. He said he knew, but he added that he couldn't resist touching it. I have never lost a point with it being all leather - because judges are not supposed to touch the car. Therefore they don't know, they don't think about it and they have no way to determine if it is vinyl or leather.
So go with leather all over.