After paying nearly £1400 to Norwich Union (even though I'm 28, but no no claims due to company car ) I also tried Heritage:

http://www.heritage-quote.co.uk/

They increased my mileage limit from 3000 to 5000 and saved me £1000!

I drive a 1988 (f) Escort RS Turbo S2 and if I can remember I'm sure the guy at heritage say classics can be over 10 years, obviously only certain cars are on the classic list though.