Iam also with Glover & Howe and have been for 3 years now like others here being covered in the car is a must and my house insurance would'nt cover my gear for the amount i wanted (£8000) and it has to be specified.
Just looked at the Glover & Howe policy, its got a £6500 limit on theft from your car ! A 500mm & a Pro body would be above that figure.