Living back in the UK, but the Agencia Tributaria keep writing to me

Hi eveyone
I used to live in Mallorca, Spain. I moved back to the UK in 2015, however, last year and this year, again, the Spanish Tax office have written to me requesting something.... I do not fully understand what it is they are requesting.

All I can understand on the form really is that they have details of me earning here in the UK during 2016.  I have looked on the Agencia Tributaria website, but sadly it is a complete minefield.

I have no clue what forms to send off to them to let them know that I have not lived there since 2015.  I have an Empadronamiento Historico.

Can anyone help me please?  I may need a lawyer, however, I do not have the funds for that as I am disabled.

thanks