Quite a heartwarming little film and not just for the kids. John Thaw is brilliant as always (without any hint of Inspector Morse about him). The boy playing William did a good job as well though I didn't find him convincing in every scene. I loved the whole feel of the small village and the slower pace of life in those times. I also felt the scenes in London where historically accurate, as far as I could tell.
It strongly reminded me of a Scandinavian film I saw a couple of years ago called Mother of Mine. That film featured a boy being evacuated from Finland to Sweden during WW II. The wife of the family taking him in asked for a girl because (as it turns out)she lost her daughter. Getting a boy instead she completely ignores him. The fact that the boy speaks Finnish complicates matters even further. I highly recommend that film to anyone who enjoyed Goodnight Mr. Tom, it has the same feel to it.