Yes, take off the bearing cap that's the easy one. A copper rivet of appropriate size is placed in the oil drilling in the crank and turned so the head of the rivet pushes the top half shell around till it can be removed. Replacement is the reverse. Remember there is a location notch on the shell so turn the crank in the right direction
Pity you didn't get the numbers off the shells, Ebay STC4299 (Think they are standard) £21.89
Great reply, many thanks! sounds simple enough even for me to do, what pitfalls if any could be encounterd?