You can’t pay UK company tax in Spain, if it is registered in UK then it is liable to UK tax. As far as Spain is concerned you are not self employed here so you don’t have to pay autonomo.
You are considered to be a tax resident if you spend more that 183 days in Spain so either don’t or pay in the UK and the Spanish won’t hassle you (yet anyway) but even if they do and you can prove you have paid UK income tax they can’t tax you again.
However you might find the Spanish system is cheaper! there are more allowances like a mortgage for instance (if it is on your primary main residence)
Suggest you see if you settle in Spain first - tax is not a day 1 issue…...............