Hmm! I think you have been given some bad advice. A cat is very expensive and the exhaust guy you have been to may be trying to avoid the expense, or at least trying to win your work with a cheap price. Removing the cat, if you are not looking for more power but looking for a quieter sound, is a bad move. The cat also acts as part of the silencer system. If you don't like the sound it may be that the exhaust has already been changed for something non standard.
I would suggest you may be better off talking to a Morgan dealer and getting him to check your system and tell him what you want to achieve.