Is there a way to set the default font for all Label text?
You can change the font for all existing labels on a page by selecting them together and changing it in Text Style. If you select a the Label tool and then change the font you can change it for all labels going forward. If you want to change the label font for all future projects, make your own template with the chosen font.
You should have your own LayOut template anyway that includes the desired fonts for text, labels, and dimensions along with your preferred styles for label leaders and dimension lines/arrowheads. It should also include things like paper size, title block, your company logo, boilerplate text, page borders, and page numbers. You should also create layers for entity types and before saving the template, make the layer for SketchUp viewports the current layer.
I have changed it for the Label tool but it defaults back to standard when I use it again
Do you mean when you start a new file?
No. I have used it in the open file and changed the text font.
Did you change it on a label that was already placed or did you change it just after selecting the Label tool. Changing the font for an already placed label only affects that label. If you want to change it for all labels you place, you have to select the Label tool, change the font and then place the labels.
Changing the label font after placing it doesn’t affect the font for subsequent labels. Changing the font before placing it does.
Thanks Dave. That has sorted it. 2 for 2!