codeine and alcohol are both depressants of the central nervous system – too much of either can make you pretty ill or even kill you if you're stoopid (stopping breathing or drowning in vomit are both capable of ruining your day)
in "sensible" amounts combining them won't do you that much harm; the effects ARE additive though so sensible is quite a lot less than yournormal sensible alcohol amount (60mg codeine four times a day is a sporting dose – easily enough to make some people very drowsy and usafe to drive, for example, even before you start boozing). Plus, the combined effect may well (though variable) make you feel pretty grim and makes some people throw up a lot (might I suggest that'd be bad for your back?)
alcohol & paracetamol: unless you're a very very heavy regular drinker, alcohol won't affect your safety if taking normal doses of paracetamol – they're mostly dealt with by different enzyme systems (If you're a BIIIG drinker, the toxic/fatal doses of paras can be lower than if you're not a drinker for a couple of reasons)
If you take the codeine for any length of time you can pretty much expect to get constipated, which I'm sure is also great fun if you have a back in spasm too. Watch out for it and consider taking something to keep things moving if you do take for any longish period