Nicky - I sympathise with your agility experience; spaniels of both genders, entire and neutered, can be a challenge; I have struggled with both of mine (one entire dog, and one spayed bitch
)
I agree with the comments made about not using a pet dog for stud (it can change their outlook on life, and only the most exceptional examples of the breed in terms of health, temperament and conformity/skill should be used in breeding programmes) - I am not as keen on the "chop 'em off" approach as some
.
Keep working on the bond between you, and in the long term, weeks or months, he is likely to refocus on you whether or not he is castrated
I never thought I'd get to the stage when I could take Molo to a unfamiliar grass course, and run him without fault at a display; he was too keen on finding scents to follow - but we did a few weeks ago, after nearly two years of practice, and I was SOOO proud of him