Andrew Barnes wrote:

Hi There

As a strict DIYer i would like to calculate the size of beam required to
support a wall, when I make a 2m wide opening in a wall.

I am an engineer, but have been working in science for years, so don't know
where to start!

Can anyone offer any help or advice?

Aye - Tony Bryer will be along in a while, but until he's here I'll plug
his allegedly excellent SuperBeam program, which you can get a
fully-functional print-disabled version of at

http://www.sda.co.uk/sbwdemo.htm

More design factors than you'd ever considered ;-) For such a relatively
tiny gap, you'll prolly find a simple off-the-shelf part at your local
Jewsons which is more than adequate. But that's just me handwaving...