Findaproperty.co.uk and rightmove.co.uk are excellent for the london area, and you can also then ask for propertys within a few miles so it will be really helpful to help you understand what towns are closeby, and will prepare you for what the average rental price should be.
Rented is common, yep, literally, everything is supplied right down to a set of cutlery, including all the essentials such as the refridgerator and washing machine, so you will just need to bring the things that make you feel at home, such as towels and nic nacs to make it personal.
This is also a great site, as it tells you abit about the actual area
http://www.viewlondon.co.uk/search.aspx?q=bishopsgate
and abit more info for ya here
http://en.wikipedia.org/wiki/Bishopsgate
Very best of luck with your move, and personal recommendations are invaluable, so try to speak to your new work colleagues before you come over and find out the best areas around you to live and play