It seems they've been in administration (insolvent) since last year. That may explain why service wasn't so great this year. The administrator has been running it since end of 2023.
I wasn't far off the mark mentioning Network Rail. From the administration document it looked like they owed Network Rail over £750 000 in rent. When I said I didn't know if Network Rail was a good landlord, I was being a bit kind. I do sort of know that they have been guilty of massive rent hikes on property in London. Many small businesses (mechanics, bodyshops, fabricators etc.) in London rent railway arches from them all across the city. Not saying they're at fault in this case though.
Running a hotel is a tough game to make work financially. There's so much competition from the chains and their economies of scale that independent operators will find it hard in the current climate without a bunch of foreign investment. It makes me think of that thread recently where the OP had a poor experience at an independent hotel in London recommended by Rick. An example of same I think.
I'd be surprised if another hotel didn't open fairly quickly after Grasshopper closes. It must have been fitted out as a hotel just a couple of years ago and I think the landlord will be keen to get another tenant in.