The nurse who took your bloods/pressure may be the culprit - while I don't believe they can prescribe meds, they can get the "duty doctor" to sign a prescription off without the doctor seeing you (it happened to me only last week with Amlodipine - the practice nurse took BP, then got the "on duty" doc to sign off the prescription (presumably) based purely on her word because he never saw me.
It may be they have a preference for using certain drugs, or the ones you have been on are contraindicated in the elderly and there are guidelines recommending switching. If you put the names of the ones you were on, and the new ones I can look them up for you.