Hi jkjjpc,
I hope this response isn't too late for you. We have been here about 15 months. I also work in Canary Wharf. If you are thinking of living in the city, I don't think it's feasible to send your kids to TASIS or ACS, which leaves ASL. Having said that, ASL is a great school, but you might find it hard to get into on short notice (at least we did!). Also, if you are open to it, there are other International schools in central London that might be an option.
If you do decide to live in the 'burbs, I think you will find TASIS to be a great choice. We chose to live in Walton on Thames for the "quick" commute times. While TASIS families tend to be spread out mostly West and South of campus, the majority of them tend to be in Virginia Water or Sunningdale although that adds 20 minutes each way to your commute. Quite a few also in Weybridge, Walton, Egham, Ascot, etc. Woking has the best fast trains in Surrey County and is within TASIS bus service radius.
ACS Cobham, ACS Hillingdon, ACS Egham are also good choices and all of them will give you kids better attention than most public schools back home. In the end, we loved the small college feel to the campus at TASIS. We are very happy with our choice. After only 1 year, our kids have pulled a 180 on that topic. A year ago today, they couldn't wait to go home. Now they are asking me if I can get my assignment extended.
Good Luck!
Eric