I found the following 7100 Specific contact information site for UK
The main support site for UK is
Thank you for the reply, I have confirmed the correct paper size is selected and feed as described in my first post so I guess I need to contact your support. Do you have a UK based number I can call please.
Thank you for using the Xerox forum.
If you have not already resolved this issue, we suggest you search our online knowledgebase for this product
Since you are not having an issue from Windows OS then you know the tray setting on the printer is correct.
The difference is the application page setup and the driver settings.
Please review the print driver paper size settings and the page and print properties in the application to ensure they are correct.
Alternatively, you can visit our Contact Us page for other support options. Our product trained experts can guide you with specific Mac setup options.
I have a client with a Phaser 7100n single draw config. He's using the casette for A3 and the Bypass feed for A4. All work as expected on a Windows 10 machine, but on the Mac OS 10.10.5 unit, the prints fail to come out at A3 size but are scaled to A4 instead.
I have tried the Apple auto download Xerox drive, I have also tried the latest drive from the Xerox support site (ie. here) and this has not changed the issue. I have also tried selecting the cassette feed manually in print dialoge options. As too I have tied various combinations of manually seleting A3 and Cassette Feed in the print options dialog.
I have also tried setting the default page size to A3 in the printer admin page going to http://<Printer's IP Address> etc.
I'm totally at a loss. Any ideas greatfully accepted.