A senior London sleep doctor informed me (on 21/03) that:

As far as we are aware, IH and narcolepsy not at increased risk. For OSA, there are some issues if using CPAP while symptomatic, theoretically making spread more likely, but the bigger issue is of comorbidities like hypertension and heart disease associated with OSA

If you have other comorbidities, then talk to your doctor and/or observe the self-isolation rules strictly.  That in itself should not be too much of a problem as IH has always been an isolating illness.

Of course poor sleep will not help your immune system, so follow all relevant advice and stay safe.