whats next

I am a Spanish citizen living in the UK since 2014, I have inherited a 25% of a pension fund my father had in Spain before passing away a few months ago. The company holding the funds are asking me to present a certificate of tax residence in order to release the money. I've read the double taxation agreement between UK and Spain but I am unsure which article applies to my case. To give more context, in Spain these funds would be treated as income, not as an inheritance, hence why I think maybe articles 20 and 22 apply to this situation. If you could provide any guidance that would be much appreciated. Kind regards,