Spanish Prime Minister, Pedro Sánchez has announced that travellers from the UK will need to provide a negative PCR test or proof of full vaccination to enter Spain starting 1st July.

Here is a link to an article in El Pais (in English) covering Sr Sánchez radio announcement this morning (28th June)
Travel to Spain: Spanish PM announces travelers from UK will have to show PCR test or be fully vaccinated | Society | EL PAÍS in English
The Balearic Islands are the only region that will move to the UK government’s green list of countries and territories, which are considered safe for travel.As of June 30, travelers from the UK will not have to quarantine for 10 days upon their return, although they will still need to take a Covid-19 test on or before day two (and quarantine if the result is positive).