Insurance for all modifications

Just wondering does anyone know of a company that will insure beyond the market value of your bike.

My bikes market value is 1500 quid less than the extra work I've put into it and thats before the current list is got through this year!

would be nice to know that if my bike got stolen I would get back its 'real' worth and not its 'paper value' which doesn't reflect its true value.

My insurance company said they would't

any thoughts - if none then we should start are own!