I few my Phantom  2 yesterday for the first time in a few months.  I noted that the altitude thatit was sending to my Feelword monitor was out by at least 7m but the horizontal distance from the controller was more or less accurate.  Checked the height using my Inpsire and it proved the Phantom was showing incorrect height.

Would this suggest a problem with the barometer in the aircraft ??

It may not be a problem. There have been a lot of reports where the altitude showing at take off was off by a few meters. I have two Phantoms and the both do not indicate the correct altitude close to the ground. It seems when the gain altitude they adjust a little better. Not 100% accurate but better. I allow a little error so when I set mine for 200 ft, I figure any where between 190 to 210 is probable close. Not an exact science...

mine's always been out by +/- a few meters, just make sure your RTH height is set sufficiently to allow for it.

Thanks for the feedback guys, appreciated.  

Don't use the Phantom much now since getting the Inspire in January, but still nice to have as a back up so I do like to keep my skills up in flying it just in case I need to use it.   I also have it set up with a Futaba controller so it requires a little more Piloting skill as you have to manually set the neutral hover position when required and the controls only need very small adjustments.  Certainly makes flying the Inspire sweet afterwards though.