If the appliance has only two wires it is likely (unless it is really old) to be class II
Answered by Sarah, Electrical Safety Expert
If the appliance has only two wires it is likely (unless it is really old) to be class II. In which case it does not matter which is live or neutral. From research on the internet the black wire is most likely to be the live wire in this case.
We do not recommend that you carry this work out yourself unless you feel that you are competent to do so. If you do decide to change the plug yourself, check that the appliance is class II if it has only 2 wires and ensure that the appliance is compatible with the UK supply voltage 230v 50Hz.
If you are not competent to carry out the work, we would always recommend that you use a registered electrician. This gives you the peace of mind that if something does go wrong, the work is insured and their scheme operator can help you if you are not satisfied.
You can find an electrician local to you here.