I'm not sure if it's sarcasm or not, but asking people to work on weekends means crossing the line, whether it's expressed in a direct or indirect way.
Apparently in USA ~50% survive year 5 of businesses. I see similar numbers for UK.
eg https://www.researchgate.net/post/Most_Start-up_Businesses_F... for USA
>Again, all I'm asking is if the startup is very clear about expectations going into the role is that ok? //
Absolutely! The truth will set you free.
I'd be curious as to what work laws in UK says.