If you wish to sell internationally opt out of the Global Shipping Programme and set your listings up with an international postage option so that you can receive payment for items you are selling in the event that a buyer from overseas purchases one or more of the items that you are listing for sale.
As of Tuesday 29th December 2020 the International Incident Bulletin on the Royal Mail's website stated "Royal Mail and Parcelforce services to Europe have been reopened and are now fully operational. For items posted today, customers should expect a delay of up to two working days for some countries. We're working with our airline and postal/courier partners across the globe to maintain services; however, delays should be expected. Many countries have implemented special measures to combat the spread of coronavirus Covid19, especially for signature service, to maintain social distancing. The number of countries we can access is changing daily."
In light of the above information you should be able to offer an international postal service that includes Spain if you opt out of the Global Shipping Programme and use Royal Mail instead; however, given that the information taken from the Royal Mail's website states that the number of countries that they can access is changing daily it would be wise to keep tabs on this regularly so as to keep track of which international destinations you can and cannot offer postage to.
Finally, if you do decide to take the advice given here, then I would also suggest extending your despatch times. If you extend the despatch times on your listings whilst still making an effort to post all items out as soon as possible after having received payment then it'll give you a bit of extra stoppage time in the event that the item gets delayed in transit, which may well prevent an Item Not Received case from being opened against you, as customers cannot open an Item Not Received case against you until eBay's latest estimated date of delivery has passed. Even if the item arrives later than it would have done prior to Covid19 then so long as it arrives before the latest estimated date of delivery your overseas buyers would have no justifiable reason for opening an Item Not Received case against you. So long as you used a fully tracked service with which you could prove successful delivery and receipt of the item in question you ought to win any Item Not Received case opened against you.
