@ Neil,
Some excellent thinking and just what I need
I will need to study this for a while and revise my thinking 
@Walter,
Thanks Walter, I vaguely remember a discussion like this, I think on WWI. The only problem I see is my hourly rate. Do I set that @ minimum wage, around £8/hr or say £15/hr.
I have noted both of your replies and will now amend the sheet ( and my thinking ) and will come back when I think I am sorted.
I can see where someone can make 100 pens a week, he will be looking for a good return on his work as I would consider that a full time job. But that would only indicate, roughly, a pen every 30 minutes or so. If I take an hour to make a Slimline Pen it doesn't matter that I may have spent most of that hour sitting in the garden with a cuppa and a choccy biscuit.
I am doing what I like and only selling because everyone I know has a pen or a Pot Pourri that I made. I am looking at a balance here, I don't want to undercut the professional, and I doubt if I could ask for more than £15 for a Slimline Pen, equally I doubt very much if I could get £45 for an Omega (especially as we don't have joined up writing here
)