Glad you felt able to tell your story here; it is so important to get it off one's chest, and most guys find it a help to do so.
You mention "putting a lid on all these fears". Unfortunately that does not get rid of them and, as you have found out, they can come out in other forms - in your case the social anxiety of peeing.
You say reading this Board is making you more anxious and not less. That is not unusual; after all, if you have found a way of living with your paruresis, and so not having to think about it much, reading this board may be bringing back the memories of bad experiences. But the fact that you have been looking, have found the UKPT, have read this Board, suggests it is a nuisance that you want to do something about.
Hopefully from what you have read, you now know that CBT is the recommended approach; and that it is the approach used on our workshops. Our next one is in September - if you are quick you can still get a place on it. So many guys come on the workshop and say at the end that they had found out about them years ago, and are kicking themselves for not coming along then, instead of suffering with it for the intervening years.
Have a think and get back to me.