Restless legs are a very common withdrawal symptom, I've never had it though.
After talking about all this with a social worker, both the diphenhydramine and the codeine, she suggested I try an over the counter product called Syndol to help with sleep, I looked it up and it contains...yup, codeine. I'll stick to Ovaltine, thanks! I have also been known atm to get up, pay all the bills online and clean the kitchen floor if I can't sleep 
I too was a furtive customer at many, many, different chemists... I even made sure I had a different coat / shoes / bag / hairstyle / hat
I would make an excellent spy.
Do make a list of things you can do for yourself to replace that fluffy warm feeling of the painkillers. Bubble baths, reading, creative stuff, drawing, writing, crafts (I craft zombie felt creatures and buy flowers and plants and have ridiculously long baths)
Sounds a bit soft but it will see you through those cravings of 'oh ffs can't I just have some more drugs!' The craving will come, and then pass, if you think, 'bugger that, I'm not going there again.'
Oh and coffee is the worst for anxiety - even if you don't suffer from it normally. I love it too. But once a month is all my nerves can handle! I am a dedicated drinker of hippy teas now!
I'm glad your dh knows, I wish I had told my dh about the nytol straight away, but I was so ashamed.