Hi Seanid,
Had the exact same problem on a 03 1.6 Focus. I had tracking and balancing done by 2 separate tyre fitters to try and fix this problem with no result. I then went back to the Ford garage where I bought the car. They said balancing was OK but that I needed new tyres. I was very dubious about this and just drove the car for another 6 months with this annoying vibration. Anyway had to get the car NCT'd last and had to replace the front 2 tyres, and now the car no longer vibrates. I drove to up to the west last weekend and the car have never driven better. You problem could also be tyre related.