Had similar the other day....On single track roads there is section 155 which does suggest... "Give way to vehicles coming uphill whenever you can".
However on a normal two lane carriage way section 162 & 163 apply.
162
- the road is sufficiently clear ahead
- road users are not beginning to overtake you
- there is a suitable gap in front of the road user you plan to overtake
163
- Ovetaking would apply where you must give way to oncoming vehicles before passing parked vehicles or other obstructions on your side of the road.
However once you have made your manouvre you would have thought the other driver would have made allowances.... sounds like they were just another one of those inconsiderate "I own" the road type of drivers. Glad you didn't have to make any claims.