not sure what i am doing was thinking about just getting rid of it has any one had the after market one stolen from there cars
the police said try my insurance company
Your insurance company will almost certainly write the car off, the cost of repair to the insurer will probably be more than the car's worth. There are currently loads of otherwise perfectly good mark one Jazzes going through salvage auctions minus their cat, some lovely low mileage ones too.
It's possible that an aftermaket cat may put off some particularly clued up thieves, but I still think your average numb nut will take them all and weigh them in. Although aftermarket cats are only worth a small fraction of genuine ones, they are not completely worthless.
The only thing you can do if you go the replacement route is fit a guard or alarm, one of the many DIY solutions suggested on here, or at least get some 'cat alarm' stickers in the windows.