Thanks Brian. Well the shoestring looks best to me in your example to be honest. Maybe I should give that a try.

I'm struggling to get what I want from the shader tree as it is. This image is with 25% fresnel (transparency and reflection) and 1% refraction, but this time I changed the angle of the light to simulate the lighting on my real glass beside me. I hoped that was the problem but soon found out I was mistaken, as you can see. I've tried decreasing the refraction to under 1% but I think the problem lies with the fresnel effect. I tried increasing it to 50% but I just get darker lines either side of the glass. It's as if the fresnel is affecting one layer of transparency but not both, therefore creating a bowl effect. The inside of that glass is not rounded at all yet the refraction makes it look more like a vase than a pint glass. Could it be that the fresnel is not going through two layers?