The Thatcham team have insured our cars for years, apart from a weird time with a V8 Discovery 3 that they were really pricey on. Rang them first when the Boxster was bought and the premium was £350 or so, didn't even think about ringing around at that point. Didn't know about the discount then... Doh!
I have also had to make a claim in the past and they were dead easy to deal with, I recommend them.