Hi Polly,
Welcome to the site, you need to save exactly NOTHING, these are major faults, as such under the sale of goods act, ANY major fault within the first 6 months of ownership is down to the garage.
This is nothing to do with extended warranties etc, but is the LAW, you are also really entitled to a courtesy car FOC whilst they yet again attempt to fix yours properly.
There is more of this attitude more and more from main dealers, it's thier problem, the LAW is on your side, stand your ground.
Don't be fobbed off with it only appies to new cars, this is garbage.
As to the fault codes,
P1361, P0620, relate to the alternator, this is the unit that generates the electricity the ca rneeds to top the battery up and run the lights engine etc.
What the faults actually mean is it is not doing what it should, as it only supplies electricity, it is either supplying an incorrect amount or none(battery would go flat eventually), the problem is on your car unlike older cars is the ECU(electronic control unit) manages how much electric it puts out, this ecu is also what controils how much fuel goes into the engine and all the ignition requiremnets(spark plugs-used to ignite the fuel air mix), easier to think of it as the brains of the engine a mini computer, so could be costly and involved if ecu is duff, hence the fobbing off they've been doing.
P0420 catalyst, this is part of the exhaust system, that effectively cleans up some of the nasty gasses that come out of the engine/exhaust, this could be duff, as it is not working as effeciently as it should, ie not as wella s it should.
B1600, is a complete mystery as to why this comes up, it relates to the PATS, or as they call it the passive anti theft system.
This is the imobiliser that stops people from stealing your car, the ignition lock has a ring around it that detects the chip in the ignition key, so when it sense the correct chip/key it allows the car to start etc, if the key is not recognised the car should not start.
This code and others may be old codes that have not been cleared.
This is 100% DOWN TO THE GARAGE, and FREE for you.
tabetha