From comments on the webcam, one chick was seen briefly on Sunday - but they both left the nest yesterday. I have only had a couple of quick webcam views today, they are in an area of longer grass so I haven't seen the chicks: one of the adults has always been sitting down, probably brooding as the weather is cooler. There is another pair nesting at Slimbridge, but I haven't seen them and know no further news.
The GCP website says that 2 pairs nested in the Somerset Levels, but both lost their eggs to predators.
I checked the webcam again before posting this. I saw Monty stand up and both chicks were revealed, having a disagreement as crane chicks do
From what I can gather, I'm presuming that despite high hopes, there has been no successful breeding of Cranes at either Slimbridge or on the Somerset Levels(where two nests have failed) in 2015.
The Great Bustards on Salisbury Plan actually bested them this year, having, for the first time, reared at least one chick to fledging stage- though it was hatched in the foxproof release pen so its growth period was largely predator free.