Charles P wrote

Thank you for all the replies, the circle method worked with some goading. I placed 12.5 radius circles along the spline with intersections being the snap option, interestingly the snap worked along the spline where the previous circle intersected with it except for one point, which I can't work out why. Here I used the "Snap on Entity" option and approximated the intersection manually.
Then I deleted every second circle to end up with 25mm dia full circles, and was able to divide the spline at each circle intersection. Measuring these individual spline segments I found that they were all under 1mm over my target 25mm length, which is fantastic! This was a great solution.
BTW I am using Windows 10 and LibreCAD 2.2.0.2 (installed only last week).