[equivalence]

This all seems to me that you were trying to hire a machine. They will work on weekends and evenings without too much complaint, but form my experience as an employee, there are very few humans willing to work those kinds of hours and be happy about it. On an odd occasion when needs must, yes, but every day and every week will always lead to the inevitable. For most people (and maybe even more so in the UK), working at a startup is just another job, maybe not to you, but to them it will be. I also found as a PhD student those who worked longer hours never finished any quicker than those who enjoyed their time a little more - this is only my personal experience though. Maybe one of your biggest mistakes was not understanding people as well as you think you do - I dunno.