If your partner is receiving UK Pension he can get his healthcare transferred to Spain by using the S1 healthcare scheme which is paid for by the UK government. Depending on which area you live in Spain and income you have could result in free prescriptions or 10% of cost.
You mentioned "partner" so if you are not married, you, being under pensionable age will need private healthcare and have to pay full price for medicines etc.
Prescriptions are available through your doctor as they are in the UK.
You will need to look at all the requirements for income and healthcare to obtain a visa to live here in Spain permanently.
Here is a link to the Non lucrative visa. There is all the information you need about income, healthcare and other documents that you will need to submit.
www.exteriores.gob.es
You will need to submit your application forms to your nearest Spanish consulate.
Steve