Holy mother of crap, I don't think I paid more than £60.
Consider cancelling your policy and changing to Greenlight - £50 a track day and your excess doubles for the day (£250-£500).
....Greenlight don't insure for Nordschleife and I don't think they include Castle Combe either.
The 'Ring isn't exactly a track day now, is it!?
But yes, you're correct and they along with pretty much every mainstream insurer will exclude it by name. You need a very specialist policy for that.
Combe is excluded by GL, given the fact its like driving through a forest and they've had so many claims over the years - I can kinda understand... but everywhere else is fair game!!