Triryche, Problem solved via our previous discussion and your recommendations. Linked amp to pc via cable and downloaded & installed Line6 Utility. The amp had been supplied with firmware version 1.00. Upgraded to firmware version 2.10 following all easy to understand instructions and once installed on amp it automatically updated the remote app. Now working exactly as it was intended and I must admit to being impressed. Great little piece of software! I'm putting a newly acquired 'Richie Cotzen' signature Telecaster through the system and the results are awesome which is slightly ahead of my skill-factor but hey, who cares!
Many thanks again. I'm sure I'm not the only new owner of a '75 tripping across this old firmware issue so it's a simple solution. Hope it all helps somebody else.
Regards, Phil