Yup, as Lyonaria said, coming directly into the UK will require the dog to be in the hold.
You can get around that by flying into Paris or Amsterdam and then driving to the UK. But I'm thinking 17 pounds would be too big to be under the seat in front of you?
If it makes you feel any better, I brought two cats to the UK. I was SO NERVOUS about them being in the hold. My vet assured me it was so much better for the animals than being in the cabin. Really big crates, the hold is dark and warm, the engine soothes them to sleep. The cabin is bright and noisy. All they see is feet and the carts going up and down the aisles. I felt like he had a point. My kitties arrived safe and sound. It was MUCH more traumatic for ME than THEM.