Engine Coolant and remote locking

[dm1996]

Hi All,
I bought my car about 6 months ago, its only 5 years old and had less than 40k on the clock. At first I had two issues with the car, the engine coolant light was coming on even though it had just been serviced and remote locking with the buttons in the car was hit and miss, sometimes they'd work other times it wouldnt, same with taking the key out, it wouldn't automatically unlock the doors at times. 
I took it back to lookers and they spent around 3 weeks in total with the car (locking was meant to be fixed first time and wasn't.) I just recently topped up the coolant as it needed topping up however it's still warning me now 1/2 times every journey I make. The remote locking seemed to be fixed for a few months but the past 2 months it's been that bad that I've had to just get in and use the lock on the key to lock and unlock the doors.
I was wondering if this is common or not and how to try and fix these issues
Thanks

[Big Dave2]

Regarding the key, if you've got a spare one, try using that for a while to see if the fault reoccurs.

Process of elimination and all that.

Is the car still losing coolant, or are you just getting the low level message?
If the latter, it could be the sensor in the tank.
If the former, then it needs a pressure test, and also a sniff test of the coolant carrying out to determine where the leak is, or if it's pending head gasket failure.