Not seen the Tyrell or the Change before. Both are interesting. Tyrell is kinda halfway between a Brompton and a Helix in terms of folding approach and tyre size (18") but without the refinement of either and by all accounts doesn't ride as well as a Brommie. Change is much like the Montague in terms of fold and requires removal of the front wheel.

None hit the sweet spot, for me, that Helix will - really elegant and practical fold/unfold, nearly as compact as the Brommie folded (same width and height, just 3" longer), normalish geometry, 24" wheels good for mild rough stuff, as light as the lightest Brommie, rolls on its wheels when folded,10 speed (in my case) but easily changed to single or 11 speed Alfine, aesthetically and mechanically pleasing, and a bargain for what it is imo. Remains to be seen what ride and reliability are like. And tyre options.... hmmm.

Yes, i know, it is not available yet - it will be, soon enough.