My motto has always been 'if you dont use it lose it' As you arent considering moving for a couple of years you can do the de cluttering gradually, start off in one room and bag up stuff youve not used or worn for 3 months and send it off to the charity shop. Also have another bag for the tip.
Wow! Two whole years-you could procrastinate for a long time. . . . Mumsy has the right idea. You could do a whole morning-no slacking now! And do a whole drawer (from anywhere) every day. Have your waste bin to hand. And get stuff off to the tip pronto before you can change your mind. We regularly have charity shop bags through our door so if you have that service you could just put it out. Let us know how you get on. . .