Without a doubt, sell the car. Keeping it for 2 years is insane. Plus in 2 years, used car market may well have corrected itself and prices returned to normal. I know someone who didn't move their car for a year, bar starting it and driving it couple of kms a month. After 12 months, a host of issues with the car. You also may go abroad for longer than you think.
You are looking at storing it, taxing it, insuring it, getting someone else to drive it a little bit, start it from time to time......and all because you aren't getting the price you "think" it's worth. Advertise it on Carzone, Adverts, Donedeal etc and give it a week. The car is worth whatever people are willing to pay for it. You might value it at €30,000 but if it's robbed in the morning and burnt out, you will get the market value of it or the replacement value. You won't get what you "think" it's worth.
This seems like some amount of unneed complications and hassle. There are more important things in life to concern yourself with. Enjoy your experience abroad for a few years.