Insurance query

[ArtVandelay]

Been looking at getting a kit car for my 21st birthday (as a present to myself) and have had the odd internet quote with Flux. The policy is with me as first driver and my brother (26) as additional driver as it will be stored in his garage.

Now I looked at car engined kit cars, and had a few quotes around the £400-500 (when I'm 21) for a limited mileage policy (2000)and stating the cars power to be a high estimate of 170bhp. Whilst looking at other options, I figured I'd try a bike engined kit car out, as there is one for sale not too far from me which took my eye. The car in question is a Fisher Fury/Sylva Phoenix and has a fireblade engine. When I got the quote back, it was £1300 with exactly the same details. Here is a link to the advert http://www.pistonheads.com/sales/1952791.htm

I know there are other companies to try but as it's purely an idea in my head at the moment, I didn't want to waste anyone's time. Is this the norm that a bike engine will cost significantly more to insure than a car engine with more power? I'd ideally like to spend less than £600 on insurance as the car will be a purely summer/weekend toy as a treat to myself. It will also be my second car. Also, can anyone recommend someone who might offer me cheaper insurance for my age. I did consider insuring the vehicle 3rd party but usually I find this to have a minimal effect on the quote whilst increasing the risk of leaving me out of pocket substantially.

I've not even been in a kitcar before but the idea of something lightweight and fun for relatively little cost (in all respects) really does appeal.

Thanks in advance

James