SallyEZ
There are a few QF UK flight attendants that commute from other countries (France, Spain, Italy etc....). There are 3 routes we do - Hong Kong which signs on at Heathrow at 10.50am, Singapore signs on at 2035 and Bangkok signs on around the same time as Singapore. As long as you can make it for sign on it doesn't matter where you live. Obviously Hong Kong sign-on will be harder to get to as it's a morning start, commuters tend to fly in the night before and stay with friends.
When you have a reserve month (being on call) you must be within 90 minutes of the airport. That is from when they call you for a duty they give you 90 minutes (sometimes more others less) notice. Here is where you might need to arrange accommodation in London.
Hope this answers your question. It's a fantastic opportunity to live somewhere else. Those that commute love it.