Can I require my staff to inform me should their circumstances be such that they need to self-isolate?

Yes.

Workers (and agency workers) who are aware of the requirement to self-isolate and are due to work during their isolation period at a place other than their designated place (see below) must, as soon as reasonably practicable and in any event before they are next due to start work within the isolation period, tell their employer that they are self-isolating, and set out the start and end dates of their isolation period.

Clear communication to all workers about their obligation to do this is strongly recommended.