spare parts for a McCulloch 338 chain saw?

Hi I purchased a 338 McCullock chain saw in 2008 for the purpose of cutting logs for my wood burning insert stove, I have just stripped it down for servicing " I am a retired maintenance engineer " so am quite capable of maintaining my own equipment, but to my chagrin when I opened the cover to the chain brake for cleaning, the tension spring sprang out and I cannot find it any where in the garden where I had my work bench.
I Have looked in my instruction manual for a part or catalogue No. but to no avail so I would be most gratefull for any information as to where I can purchase a replacement part either in the U/K or here in France where I now live !