I tried for 3 evenings to fix this and it turns out it was the case sensitivity of the file name. It never occurred to me that that would matter on windows 10, but it did !
I really appreciate you responding.
I was aware that the xml files are a little cumbersome and prone to error if you create them by hand so i have 2 spreadsheets that take a list of waypoints, or a list of airports, and builds the xml files for you, making it quite quick to create a lot of traffic. I wanted the waypoint version so i could do a vintage air show at Shuttleworth
Once I've made them a bit more robust i can post the macros if anyone is interested but they are really basic.
I fell victim to one of the sensitivities of XML that i was trying to avoid with my macros !!