'Moving' a doorway

[bullethead123]

Hi all, I have a very small kitchen, made all rhe snaller by having a doorway to the outside yard within the kitchen. I intend to replace the kitchen units but before I do I would like to make some reformations to the layout.
There is a standard window in the back room which I would like made into a doorway and the doorway in the kitchen partially bricked up and made into a window. This would give me almost a metre of extra worktop and under cupboard space - an enormous amount in such a small kitchen.
How should I go about selecting a builder and what would be a reasonable cost for this work?
The house is inSutton, South London.

 

[robinbanks]

How should I go about selecting a builder

Word of mouth from friends who have had good work done before

and what would be a reasonable cost for this work?

What's your budget? What's it worth to you? I'd be disappointed for it to take longer than two or three days, and I'd ballpark about £3k, materials and labour (but I've a visitor's perception on the cost of stuff in London)