A couple of points spring immediately to mind and sound alarm bells... If "paying your way through A levels" and "having to work" resulted in you getting CCD - what on earth gives you confidence that you're gonna achieve a first at degree level? Surely you're in the same boat at degree level - i.e. having to work and pay your way... how is your situation at degree levelgoing to be any different???
That's the first concern.
Secondly - pipe dreams... I know from bitter and hard won experiences that "plans" rarely play out the way you want them to (and also plans that friends, colleagues and family have had). And it is also fair to say that in most cases my long term plans were never as highly ambitious as yours!
It's good to have a goal, don't get me wrong... but nowadays I just take things as they come. There are so many twists and turns along the way - the smallest, most insignificant, unexpected little thing that can have extreme and enormous impact. Having such a dedicated long term plan (getting a first, getting an LLM, becoming a barrister) is, in my opinion, ridiculous at this stage in your life. Is such a long temr plan "reasonable" - to be brutally honest, I'd say not... even the most optimisitc soul would be hard pressed to say you've demonstrated the ability.
By all means have an ambition - but please set yourself some near focussed goals. It's easier to stay on track and you're not going to be so disappointed when things go off-kilter... and they will - whether you achieve your ultimate ambition or not - you're going to have twists and turns along the way. In the first instance I'd say set yourself a goal for the end of your first year - keep the LLM, the Barrister thing in mind - but don't lay the foundations in your mind - build the foundations out of tangible results!
Sorry to be harsh.