You should check with your home country to see what their rules are regarding "tax residence." Normally, however, your tax residence is where you spend "most" of your time, where you have your primary residence (i.e. home), where you work and a few other factors.
I'm not aware of any EU country that taxes based on citizenship (normally that's only the US and Eritrea), so it should just be a matter of establishing legitimate UK residence. However, you will also want to check the tax treaty between your home country and the UK. In some cases, income maybe be taxed based on its source - say, a pension that comes from your home country may be taxed in the country of origin rather than in the country in which you live. (However, there are tax treaties that treat pensions or other specific sources of income differently.)
There is detailed guidance on the issue by HMRC of certificates of residence in the International Tax Manual starting at IHTM16200. Some countries have their own forms which they require to be completed. HMRC will need to be told the country concerned and the reason for the request.