Agreed valuations without classic insurance

I am having trouble finding an insurance company that will insure me with an agreed value of my restored mk1.

The problems i am coming up against are: -
I am only 23; and
I regularly use the car (Not insured on any other car)

I've got 4 yrs no claims, no convictions and all the rest of it but the cheapest insurance quote i can get with an agreed value is ?786.

I've tried: -
Footman James
Premium Choice
Lancaster insurance
Carolenash
Gott&Wynne
Performance Direct
High Performance
Swinton
Allen and Allen
Adrian flux
a number of others that i was passed around
and HIC who gave me the quote of ?786

they were unable to insure me either because I was under 25,  the fact it was my only car or simply they were more expensive than ?786.

Does anyone have any suggestions, is this a fair price because of my age or am i being ripped off?

Please help   

Seems a fair price if you have a decent agreed value on your motor.

AS my uncle said these MK1s walk like they have bloody legs. I found that funny.

So it is a risk for them to give you top money for ya car.