I'm from the UK and moved to Hokkaido a couple of years ago. I guess that's not really doing a 'season', and I don't work in a ski resort. But I still ski alot (62 days last winter, 64 so far this winter) and have a pretty comfortable lifestyle. Feel free to PM me if you want any info on life in Japan in general.
For specific info on working in Niseko, yeah MitchPee is a good guy, PM him. Also there is a guy called Rosbif who is a Brit who has instructed in Niseko for the past few winters.