@Con-Hennekens that is what I ended up doing and it works just fine.
When all the waypoints are actually ViaPoints (as opposed to shaping points) I tend to search along the active route which works very well but the shaping points dont allow the service station to be slotted in at the correct place.
I will have to think about how to create routes using shaping points in the future for 3rd parties as, unless you understand what is going on, it will cause problems.
Something to keep me busy on my return in a months time..