Rough how much to move my back door...

[another20]

....assume need to take out old door and frame, brick up existing opening, cut new opening, add lintel, install new door and frame.....

How long would this take - can one tradesman do this?
How mush would materials and cheap back door cost?

Best to get a couple of quotes from builders, as it depends on your house (does wiring or pipes need moved, how much of a back step you need to install and remove, what finish you want inside /outside). Plus, your location and what part of the country will also make a difference to the cost.
As a ballpark, i would guess between £2,000 and £4,000 plus decorating costs.