OK thank you for your help with this. Much appreciated. I'll hopefully get this sorted tonight. 
Thanks again. 

A CVX file is not an absolute requirement, plenty of updated AFCADs don't include a CVX file. In such a case FSX will use the default airport background.

If you post a link or at least the file name of the download then some of us can test it to see if the same problems appear.

Sometimes problems are caused by having more than one addon installed for the same airport. There's a utility called Simple Airport Scanner that helps to find duplicated addon files.

egnt_afcad.zip at flightsim.com   I'll look here also!  Yep, in the Library here, also!

23 hours ago, fshobby said:

A CVX file is not an absolute requirement, plenty of updated AFCADs don't include a CVX file. In such a case FSX will use the default airport background.

If you post a link or at least the file name of the download then some of us can test it to see if the same problems appear.

Sometimes problems are caused by having more than one addon installed for the same airport. There's a utility called Simple Airport Scanner that helps to find duplicated addon files.

This is link for the .exe file I downloaded and installed. 

http://www.arm-computers.co.uk/Airfield_Index/Index_1/Airfields_4_/airfields_4_.html

The first link is where I downloaded the scenery from. Let me know what you find out. Thanks 

 

I have just found that the problem I was having was due to a missing texture file which for some reason does not agree with my system; I have just removed that freeware addon and used a different one from another developer - problem solved. I now have a fully functioning EGNT addon airport.

Thanks to you guys who commented and helped me out here, much appreciated! 

2 hours ago, johnfo said:

This is link for the .exe file I downloaded and installed. 

http://www.arm-computers.co.uk/Airfield_Index/Index_1/Airfields_4_/airfields_4_.html

The first link is where I downloaded the scenery from. Let me know what you find out. Thanks

I took a look at this airport. The reason you get trees is that it requires that you also install photo scenery product. This is mentioned in the pdf manual:

Other Required Scenery
Horizon GenX Photo scenery Volumes 3 together with GenX Mesh

The scenery excludes the default airport background. Photoscenery will suppress autogen but if you didn't install the photoscenery then because the default background is excluded, the autogen will pop up through the airport aprons.

2 hours ago, johnfo said:

 

I have just found that the problem I was having was due to a missing texture file which for some reason does not agree with my system; I have just removed that freeware addon and used a different one from another developer - problem solved. I now have a fully functioning EGNT addon airport.

 

Good to hear it's resolved.

Thank you for looking at that in depth for me though!