Earlier quoted context omitted.
"in the course of" meaning, related to. personal work on personal time is not 'In the course of" employment. It's that latter bit that the GP is obviously asking about. The contract he linked has especially egegrious language. It's not worth negotiating IMO. Any employer that even tries to get such language in is showing their cards.
The plain reading meaning of "in the course of" is not the case law, though, it has established precedent - and most of that favoured the employers in question. I don't know of a case that took into account "personal time" as being relevant, and most salaried employees are not paid on the basis of hours worked. The typical contractual language does go beyond the established case law, but not by as far as you seem to…
In my experience salaried IC's in the UK are explicitly contracted for 40 hour weeks, excluding pensions, bonus, shares, etc.
It is only when you get on managerial tracts and C-Level that you have some form of hours exemption which means no OT and that implicitly you 'could' work 24/7.