Engine warning lights after attempted Cat theft - Insurer issues

[HeyMcfly]

Hi Folks,

Hoping someone can help.  I have a 2010 SE jazz and last month I went to start the car and the engine warning light was on and it sounded like a lawnmower.  Mid section of exhaust was on the ground, took to a local garage who confirmed an attempted theft and sent me pics of the mess that had been made underneath the car.  The thieves didn't know what they were doing and wrecked the Cat so that had to be replaced.    Claimed it on my insurance who confirmed it was worth a claim and could be fixed.

Fast forward to the repairing garage calling to say that they had repaired all of the damage and there is still a light on the dash, they said this was showing the below faults.

Maf sensor voltage low
Charging system low voltage
Heater Cct malfunction
Alternator

They returned the car to me however it came back on a recovery truck and they are claiming these must have been existing issues (car was running fine with no warning lights) and that they cannot be anything to do with the attempted theft as the alternator is too far away from the Cat. 

I have submitted a complaint as I can't use the car but wondered if anyone with more mechanical knowledge could tell me if the alternator and above warnings could possibly be as a result of the damage?

[culzean]

The CAT burglars must have been newbies,  the CAT on 2008/9 --> is tucked up behind engine  and bolts straight onto engine exhaust manifold.  Pretty much impossible to steal and in any case no real value as it has a fraction of the amount of the precious metals that the older ones have. They may have butchered the pipe leading out of CAT and made it unusable - and damaged the post-CAT oxygen sensor...   

I don't think the other problems can be connected to aborted CAT theft unless they really messed up some wiring loom that goes to / past rear of engine or where it goes through firewall into the cabin - do you trust the garage and have you used them before ?

https://www.bestpartstore.co.uk/9433401-walker-catalytic-converter