Hi Sarah
I found I needed some netting (actually quite a lot) as the local critters (rabbits, pigeons, mice) ate everything I had planted. :'((First year on the allotment and some valuable lessons learned!)
I looked on the internet for the best deal, but in the end bought from the local garden centre as I wanted to see what I was getting. I didn't want the cheap and nasty nylon stuff that I've had before which gets into a knot and is impossible to sort out.
They had a variety of types and meshes and widths and the prices weren't too bad. They come on rolls so you can get however much you need. :)
I bought some 'knitted' netting which is used to put over ponds which is 4m wide. (It was about £2 per running metre.) Maybe if you find a garden centre which also sells pond fish/supplies they may have a selection. Or look for a pond supplier on the web.
Hope this helps.
Willawiz