It is quite easy for people handy with a smartphone. First take a good selfie with plain white background and then type into your browser Renew UK Passport bring up a link to the https://www.gov.uk. site.Make sure it is the genuine www. gov.uk site. It costs 105 euros or free if you are over 90.
UK Passport Renewal at Round Town Travel Avda Dr Severo Ochoa 2, Benidorm
You can get your passport renewed here for 160 euros or 30 euros if you are over 90. They send off your old passport and you will get a new one in the post together with your old passport in separate envelopes delivered by courier. Passport renewal con now only be done online or with smartphone so those not tech savy this is a good option.
Telephone 966 811123. If you do not live in Benidorm ask in a British owned business such as Estate agent etc to see if they will do it for you.