I had this problem with DS1 and I basically worked around his schedule and made sure we were home for the midday sleep, so as not to ruin his routine.

Now DS2, the same is happening... I've been trying to get him used to sleeping in places other than his cot. So every couple of days, I put him in the pram and go for a walk for the late afternoon nap, or morning sleep.

I have found that if I put him down to sleep somewhere else in his sleeping bag (swaddle up), he will sleep pretty well, because he's created an association with it. On the other side of the coin, I need to wean him off it soon and create a new one - maybe a comforter?