Thanks for your interest. I did get round the issue but it seemed a lot of actions to achieve a simple thing. I sliced the model into 2d mode around the correct place, inserted a 2D circle, removing the line above the surface plane, then changed to 3d mode and pulled it to the correct length. Somehow, this just seems wrong to me. I can create a cylinder and combine it but I don't seems to be able to combine it then subtract it to leave the impression of where it has been.
For the most part its an amazing program, very fast to learn and pretty easy to use. I am only a newbie with this program so a lot of the features I have yet to use. Generating text is a bit of a faff. Write it in sketchup, save as sketchup version 8, then import into designspark and scale to suit with pull tool. Hardest bit I have found is then to get it to combine with the face the lettering goes on - probably missing a trick or two there.
Most complex part so far is a new x carriage for my 3d printer, piccy attached. Apart from my mistakes it turned out well.