Definitely looks too short to be able to apply a decent amount of torque. I wouldn't have cut the bit out of the middle myself, and if those spanners were mine, I would carry a piece of flattened steel tube/electrical conduit to slip over the handle to increase the length of the lever and the amount of torque.
Using your foot on the end of a spanner to increase the force is not always a good idea; I once cracked a bone in my foot doing that with a huge adjustable spanner which already had a scaffold pipe extension over it.
I have a set of stubby combination spanners branded "Forge Steel" - which IIRC came from either Screwfix or Toolstation. They won't be the absolute best quality, as they were pretty cheap, but mine have seen quite a lot of use and are perfectly adequate for use on a push bike.