If your grass area is not wide enough because you have a soil border at the side, it is possible (though not recommended) to fasten the guy ropes to a strong fence over the top of the border. This will save you the space required at each side for the guy ropes.
In these 2 pictures from the "Will it Fit" page, the shaded floor area includes 75cm at each end for the guy ropes. Therefore if the poles are positioned right at the edge of the grass before the soil, so the guy ropes extend over the soil to the fence, this reduces the width required for the shaded area by up to 2 x 75cm = 1.5m.
Read about fastening to fences click here.
On the Standard size goal only, it's also OK to shave 0.4m (16 inches) off the required width if that makes the difference. This will reduce the minimum area either side of the goalmouth to 0.8m vs 1.0m. Here's a picture of where a customer did this.