You need to become familiar with the term "Throw Ratio" because this will help you short list the projectors that tick your particular box.
Throw ratio is the relationship between throw distance and some facet of the screen dimensions; width, height or diagonal.
Screen dimensions are often quoted as diagonal and in inches, and sometimes nominal sizes too. So a 110" screen might actually measure 108" corner to corner. So it's worth checking the exact measurements and also becoming familiar with converting diagonal to equivalent width and then from inches to centimetres.
For 16:9 screens, width = diagonal ÷ (divide by) 18.35, then x (multiply by) 16
e.g 100" diagonal ÷ 18.35 is 5.45"
5.45" x 16 = 87.19"
Convert inches to cms, inch x 2.54 = cm
e.g. 87.19 x 2.54 = 221.47cm
Once you know the screen base line width and the throw distance from screen to projector lens, you can then work out the throw ratio required to fill the screen from that distance.
Throw distance ÷ Screen width = Throw ratio
e.g. 300cm ÷ 221.47 = 1.35
So, based on screen width, you need a projector with a throw ratio of at most 1.35
The same calculation is possible based on screen diagonal (100" = 254cm. So 300 ÷ 254 = 1.18 throw ratio), you just have to check the manufacturer's web site to make sure whether they're using width (the most common used) or diagonal.
The Benq W1070 has a zoom lens, so there are two throw ratios. One is for when the zoom lens is at the wide angle end (shortest throw) of the adjustment range. The other is for the telephoto end of the range where the throw is the longest. The throw ratio is 1.15~1.5:1 based on screen width.
You can do a simple sum to work out the throw distance. In your case it would be screen width (221.47) x throw ratio (1.15) = 255cm. So you know that this Benq will fit the space and give you the screen diagonal of 100".
The Benq is 1080p native and sells for around £500-£600
