Do we have to pay tax on our savings in uk or is it just on the interest. Thank you

Just the interest generated. But you have to declare the savings if you have more than €50,000 on the modelo 720.
This includes premium bonds as well. The 'winnings' are also taxed here.

Thought this might be useful

https://www.gov.uk/guidance/living-in-spain#tax

Thank you very helpful

thank you

Worth getting tax affairs in order - thought of another informative link

https://www.pellicerheredia.com/en/open-library/

see second line of brochures down

just had a look and downloaded the relevant brochure, very interesting. Many thanks