That's just insane - I've just (last week) got a new policy with Heritage for £180, 38yo and no NCB, here in Somerset. I'd DEFINITELY shop around a bit more!
And that price is including a SkyTag GPS tracker for free (you pay for the first year's subscription, but the unit's worth £250 apparently), green laning, off-road events non competitively, all mods etc etc.
Prices did vary a lot though, but worth talking to a few of the obvious 4x4 specialists like Carole Nash, Lancaster, Adrian Flux, and Heritage. Heritage were extremely helpful I must say. A bit slow on sending the actual documents out but they were a bit swamped at the time. I'm waiting to get a valuation for an agreed value cover on it, will be interesting to see what they come back with.