OK then.
He is on IS, so he is fully exempt from the habitual residence rules in their entirety: HB Reg 10(3B)(k) (and its equivalents in the 60+ and CTB Regs).
All the other factors you mentioned only become relevant if Reg 10(3B) does not apply. Whether he should be on IS at this stage is another question … it could be our old friend EC Regulation 1408/71 again. I’d just be thankful for an easy case and get it into payment before you talk yourself into contacting DWP.
