there is no such thing as a true bolt in cage, as every bolt in cage still needs plates welded to the car.
Mark Fish wise... 182 cages are around 750, or if you want him to fit it around 1200 quid mark. As its not as easy or straight forward as some people think.
It doesnt really matter which cage you go for, whether it be OMP, Sparco, Safety DEvices, Custom Cages, they all conform to the same set of FIA regulations.
Price wise, i have always found Sparco and OMP to be at the more reasonable end of the market, with Safety Devices costing a fair bit more. But then they do come painted.