1. Yes (THE RECEIVER GENERAL FOR CANADA ), you need to pay $150.00
2. Yes
3. Dont worry until they ask updated statement. But on your side be ready to show or have that amount of money in your account. You will need to show in Canadian Border. They didnt asked for statement in my case but certainly it might be different for each cases.
4. At the moment the address for London visa office is Immigration and Medical Services, Macdonald House, 1 Grosvenor Square, London, W1K 4AB, U.K please beaware from 16 December the address may be changed.