Hi Ian,
There's a few things to consider before embarking on the studding of your working boy, The biggest mistake people make is its gonna be an easy option 'advertise my dog for stud and I will be inundated with offers'. TBH there is now quite alot of competition from stud owners now and the more hardcore working kennels will usually opt for a Trial winner or champion or a very sound hard working and WELL KNOWN working stud that is working a full season (probably a popular gamekeepers dog) to line their own bitch.
Health screening is also now becoming very desirable by alot more breeders, even the hardcore working kennel's are more aware of the benefits of HS, but this is mainly due to the fact Puppy buyers tend to be more savvy now and demand more from Breeders. This can run into hundreds as there is quite a few screening hurdles to get through. The Hip scoring in workers seems to be unveiling what could be deemed as dodgy hips in many and I am aware of a few with quite high scores. Glaucoma is a problem too in working lines, Pra and Fn seems to be the topic of debate with alot of working kennels, with claims they don't exist and no problems within working lines. Even though we have rumours of pups dieing quite young from what appears to be symptoms of FN, Unfortunately we do have working cocker's out there who are excellent working dogs but they have show in their backround as well as many with a touch of other things in there to take anything for granted. And we also seem to have deafness and heart conditions emerging.
It really boils down to what you want from your own boy, maybe to invest in your own line of working cocker's which then yes get him tested for your own sake, if its simply to outbreed, 'OK' but the chances are you may never get a single lining from him as there is a hell of alot of competition out there. But as long as you are aware of the pitfalls anything else will simply be a bonus.
Good luck with him though he is a lovely dog BTW.