Ah the focus is such because it's already been 'agreed' that he'll be visiting. But it's the type of visit that could still be tweaked. Something that might be possible to do with lots of signatures. Whereas The Powers That Be are never going to uninvite him.

I saw an interesting comment by reader James Boag on the guardian article about this; it says
"Once the trump petition reaches 1269502 what does this mean for Ms May ?
At that point she will ignore more people over Trump than she's using as reason for hard brexit !"

an interesting point :)