If you think that an address where you just receive post (an accommodation address) is your address, your place of residence, the place where you normally reside, well that's fine, but don't expect most people / authorities to agree with you.
Just in passing:-
Certainly, as far as Spain is concerned, if you spend 183 days or more in one year in Spain , you are tax resident in Spain and legally obliged to pay tax on (almost all) your world wide assets and income.
I just looked on the web.
UK HM Customs say:-
Individuals receiving supplies in a private capacity are treated as belonging in the country where they have their usual place of residence. An individual has only one usual place of residence at any point in time. Individuals are normally resident in the country where they have set up home with their family and are in full-time employment. They are not resident in a country they are only visiting as a tourist.
Motoring in Spain :-
A foreign EU resident is someone who lives more than 6 months or 183 days a year in Spain and Spain is therefore their official place of residence.