A few days ago my car had a problem where the glow plug light continued flashing after car got running.

 

Then soon after the Exhaust system light came on and stayed on.

 

I have a mate who has a diagnostic tool and it ready the code PO544 and described as above.  Can anyone tell me where abouts this is located on the exhaust?  Is it an easy fit as I am not too mechanically minded or is it recommended for professional fit.

 

That's a generic ODB2 code from a generic reader.  Find someone with VCDS which will give much more information.