My b is on a "future classics"-type policy. I went with Hagerty (
www.hagertyinsurance.co.uk) on silkblack's recommendation.
Fully comprehensive insurance, agreed value £6,500, no mods, limited mileage 5,000 miles pa, car is garaged, use is restricted to social, domestic and pleasure only. Another car must be available as a daily driver. I am the only driver (>30 years, no claims or convictions, driving licence since 1991). When they asked if I was a member in any owner's clubs, I mentioned the Fiat Forum, which also helped to get a bit of discount.
Annual premium £280, which includes European breakdown cover for the year (otherwise it would have been around £250). £200 excess.
I also asked Adrian Flux for a quote - can't remember the exact figure but I seem to remember they wanted around £100 more.
The cheapest "mainline" insurance companies I could find on confused.com (but with fully comprehensive insurance and no limit on annual mileage) were Tesco Value (annual premium £535.50, total excess £575.00 (!!)

), Tesco £619, Virgin Money £633, Bell £724 - Tesco and Virgin Money with £250 excess, Bell wirth £200.
Regards
Giorgio