Cheap cover

I have just taken out a great cheap policy with BG insurance , declared lowered suspension 2.0 16v engine and alloys on a classic policy fully comp with breakdown cover (50.00 excess) for call outs all for £108.00 , the only problem is to get a agreed valuation I need to get somebody in the know to sign it to say it's worth the money ,don't know where I can get that done though !