Some possible solutions:
- Replace existing hall ionisation alarm with optical type and move away from kitchen door, if at all possible. An optical alarm is less likely to be set off by a few cooking fumes.
- Remove hall alarm. Install heat sensed alarm in kitchen. Install ionisation alarm in lounge.
The second solution probably doesn't quite match building regulations as there would be no detector in the downstairs circulation space. However, in my opinion it would be safer, as it would reduce false alarms, which are dangerous, whilst still maintaining detection in all rooms likely to have fires. A fire in the hall itself is unlikely and will set off your upstairs detector in any case.
Christian.