Thank you Wristpin. It is appreciated. I have both that exploded diagram and I have the forum post you mentioned on my bookmarks from previous searches on google. I have been researching this for a few months now and keep coming up with a blank. I have seen plenty on the Howard 350 but hardly anything constructive to do with the Howard 300 clutch system. Following further invistigations yesterday I sent of an email to http://www.howardregister.com but I have not yet had a reply.
Again thank you for your post wristpin it is most appreciated. I will keep you all updated with my progress which might be a little slow as it depends on the weather.
Edit: I forgot to add that whilst I was doing further research yesterday I read that the Howard 300 used a fibre thrust washer on the clutch so I did a little searching and found a picture of said fibre thrust washer on google images. The image lead me to a ebay listing so I contacted the Ebay seller and asked them if they will be having any in stock and where the thrust washer was situated. He replied saying that they will be some in stock maybe later this week and he included a picture of the item and the location of the fitting which raised another question. In the image there is a "Lollypop" looking item which is also missing from our clutch setup on the Howard 300. So I have sent him a reply questioning what that lollypop looking item is and if he has those in stock also. I will include an image bellow.