Visa for British National living in Spain

I am a retired British National and have lived in Spain for the past 5 years. I want to visit British friends working in Shaghai in May. I have never bothered to obtain a Spanish Residencia as this is not a requirement for EU citizens. I have a Spanish NIF number and have paid my taxes in Spain. My travel agent thinks that I will need a Spanish Residencia certificate to obtain my visa. Please can you advise.