Why not invite your girlfriend to go with you? Or find a time that works better for the both of you? I know that my wife has found going on walks with me one of the rewarding things of my new healthy lifestyle. It's a great time to share and spend quality time with each other. Having a partner or a friend involved will make weight loss easier. It makes you more accountable and is helpful when trying to make healthy lifestyle changes in your life.
Juice used as a cordial to give you water a bit of flavour is ok...better than the alcohol you are allowing (maybe you can water that down too
). You are right to stay away from junkfood shops and soda/soft drinks. That will go a long way to a healthy start for your new lifestyle. You will be surprised by how quickly your taste buds will change and thank you for not putting that rubbish in your mouth anymore. I use to gulp coke down daily in large amounts...now I really don't enjoy it's taste anymore.
Your goals are modest and doable. I wish you success in your journey to a better future.