Michael Ward Associates, who are often recommended on the Ferrari forums
http://www.michaelwardassociates.com
Mainly dealing with agreed value, limited miles policies. They insure my F355 for less than £355 on a "classics / future classics policy" which includes the elise / exige.
For the elise and the exige, each with an agreed valuation of £21k, each limited to 5k miles per year I was quoted £520 in total for both cars. As a "classics" policy it also doesn't need any existing NCD so well suited to 2nd / 3rd car situations. Might be useful for some

Jim