just got the latest firmware off the reprap site (RELEASE FILE - "RepRapFirmware-057a-16-01-2014")

When I perform the 'M105' check on Arduino 'Serial Monitor' I get the result;
serial: M105
okT:9.8 B:22.8

but when i perform the 'M115' check i get the result;
'invalid M Code: M115'

........... is this a problem???

Yes, that M115 response indicates that your Duet board has very old firmware on it. See [www.reprappro.com].

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].