Need some help with a room layout and gear advice

[scoped]

Hi there,

I'm hoping to set my front room up with a projector and 5.1 surround sound.
I thought it would be easier to just draw up a scale drawing of my room, so here it is:

Just some added dimensions:
the distance between where the projector screen is and the sofa is 4.30m
and the whole length of the room is 6.40m

I use a wheelchair, and would sit at the end of the bottom sofa, I'm a foot or so taller than the people on the sofa, so i don't know if that'll effect placement atall.

Any help with speaker placement would be good.

The projector I'm looking to buy is the benq w1070

The projector screens i'm looking at are:

PCW120GE 120" HD Projector Screen Glass-Beaded 16:9: Amazon.co.uk: Electronics

http://www.amazon.co.uk/Duronic-EPS...9TSE/ref=sr_1_6?ie=UTF8&qid=1346339980&sr=8-6

I found a thread on the second screen on avforums saying it was good for the price, but I don't know anything about the first one. So any advice with the screen would be good. I'm thinking these sizes should be ok? Or should i be looking at a different size for my size room and how far the sofa would be away from it?

Any help would be much appreciated!!

Thanks