First question you have to ask, when are you planning on retiring. lets assume 65 for now
Second question, how much is property where you want to live?
You have approx 18 years to go to your retirement, assuming your investment keeps pace with inflation and you continue to invest 500 a month then at a rough calculation you will have somewhere in the region of €175k-€200k to spend on a house when you hit 65. remember, it's unlikely you will get a mortgage at retirement, at best, it will be very difficult
I know it is only a rough estimate, but will that buy you what you need given the value of your investment will (hopefully) rise above this but so will property prices?
Is buying in the UK now an option and rent it out?