A lot of people are put off by physics - it can come across as dry and tedious, where the content is too abstract to be interesting and the calculations involve too many numbers. I am somewhat of a physics-lover, and even I found physics at school quite a chore.
From the little I know about what it is to teach, I have no doubt that the national curriculum is very stringent, allowing little space in which teachers might inject excitement. Even if there was the space, teachers tend to be so over-worked that it's hard to see where they could find the time. However, there is something I think that could make a difference; something that teachers could do that would attract students' interest, creating a foundation upon which learning physics could be more engaging.
Students listen when they see things they don't expect, whether it be their teachers put on a ridiculous Christmas pantomine or something less excusable such as their peers creating class mayhem. Physics has the advantage of lending itself to demonstrations with impressive, and often unexpected, results. So perhaps physics lessons could involve a few more things like that.
I was watching a QI repeat quite recently and Stephen Fry was describing a rather fantastic demonstration he was privy to in one of his school science lessons. His teacher brought into his class a single, red rose. Rather dramatically, the teacher whipped the rose into a bucket of liquid nitrogen and then flung it against the wooden desk, causing it to shatter, like glass, into a hundred pieces. Watching a rose shatter on impact is definitely something you wouldn't expect to see, and would have definitely got my attention in a lesson. After a short discussion on the exciting properties of liquid nitrogen (nitrogen - liquid? etc.), perhaps this demonstration could be an introduction to a GCSE lesson in cooling and heating.
I know that there are so many reasons why this, in general, couldn't be a solution to the lack of interest in physics lessons. Obstacles show up in their plenty, from the limits of technical support available to teachers to having a class disciplined enough to perform demonstrations of this kind. But the point here is that physics lends itself to eye-widening phenomena, and enabling students to realise this might make them a bit more excited about it.