I am not aware of anybody mocking you for your struggles with opioid addiction, Evey. And if anybody is they are ignorant and not worth allowing yourself to be upset over. One of the really,
really important aspects of tackling addiction issues with any real chance of success is to be doing it purely for yourself. Nobody can force another person to deal with their addictions because that in itself just becomes another reason to avoid dealing with the addiction ("It's not my problem it's other people that have a problem with me") but, for the very same reasons, nobody can deal with their addictions to "spite" or to "show" other people - again, that is simply a way of shifting the problem onto somebody else which can never work when that problem is not one that anybody other than yourself can deal with.
I know it is hard but I think it would be very helpful to you if you could try your best to not focus on what other people may or may not think about you. Ultimately it is not them who have to go through the pain - physical, mental, and emotional pain - and do the actual work of taking on addiction issues and taming them as best you can. You are the one who has to deal with the day to day reality, you are the one who has to cope with the difficulties of changing patterns of behaviour which become very deeply rooted when they've been a part of life for so long. They don't have to concern themselves with what is likely to happen if you go for this high risk strategy and (quite frankly) most probably come a cropper and put yourself in a far worse position than you need to be.
Similarly, it is not very helpful to try to compare your own situation with that of other people who have very different situations. Aside from the fact there is no way for you to really know the whole story, it also comes down to the far more basic fact that you are you and and Englandz is Englandz and Owain is Owain... everybody is different and it just isn't as simple as straigh comparisons suggest.
Try to focus on yourself and your own situation. Give your keyworkes a chance. They cannot truly help you if they don't really know what the true situation is because you are giving them a false impression. Honesty really does go a very long way when it comes to dealing with addictions. As you note yourself, lying, hiding and covering things up is a sure sign of addictive behaviour. One of the best signs that a person is really getting on top of their addictive behaviour is when they start to make a point of being completely honest with others. Give it a try - I really do think it will get you to a much better position than your current approach.
All addicts have trust issues but - much like the honesty thing - being able to let your guard down is often the key that opens up the next stage of the recovery process. Give your keyworker a chance. At worst you can always switch to a different one but seems only fair to give this one a fair go as so far s/he doesn't really know your true situation at all so how can they be expected to help you properly?
You've been doing so well recently, Evey. Seems a real shame to throw away all that hard work for the sake of getting a bit frustrated and impatient when approaching the the tail end of your taper. Even more of a shame if you were to throw it all away for the sake of "showing them" when "they" clearly don't have your best interests at heart whoever "they" may be.