It's good advice. I also have a Panasonic aircon unit with external condenser for my 2 bedroom apartment, 6 years old now. I'm all electric, cooker, water boiler, etc etc. I ran the aircon quite a bit during the days in July/August, and overnight every night. I wasn't away at all during these months. My July bill from Iberdrola was 74€ and August 77€. Which I think is well worth the comfort.
In the winter I'd recommend floor rugs and curtains, plus insulation strips for windows and terrace doors. Check under main doors for draughts and put excluders on them.
I top up the heating in winter with oil filled radiators in the bedroom but use sparingly as they're quite expensive to run.
Kind regards
Steve