Not a stupid question at all, but I'd suggest that you're doing very well with the quotes you've got. I paid around £170 in the UK for an agreed value policy; 4k miles; garaged, etc. The policy in Germany gave greater freedoms (not that I needed/asked for them) but cost about three times more, plus the car needed a 'professional' third-party valuation (which was a complete joke as it turned out; the guy they sent me to knew nothing about the cars).
The US is not cheap for classic car insurance, either. I think here I'm paying about $500 for the most restrictive policy I've seen. Agreed value again, but not requiring a third party valuation. To date, the UK cover has been the best and cheapest.