Cabin heater problems

[Steviep351]

Hi Guys,  new to forum and looking for advice.

 

Car,   54Plate  XJ 3.0 V6 SE.    

 

Problem,   the cabin heater does not heat up as it should,  if giving the car some pedal the passenger side will get warm but drivers side nothing when normal driving nothing either side.  I flushed out matrix and back flushed it and topped up coolant.  Took it for a run and still the same.  

 

I have to go somewhere in a cpl of days and worried,  my daily drive isn't more than around 30miles but I'm going on a 500 mile round trip and all though car runs at normal temp from temp gauge I'm worried with cabin heater not working and no air in system will it affect the engine ? 

 

When time permits i will get to bottom of cabin heater unless someone knows why this happens ? 

 

Advice greatly appreciated