I was wondering getting a 1000w flood and of course fitted with a 1000w MH but the current it pulls would be at least 7.5A on MV ballast. So the current is a usually doubled without PFC so I guess it would trip the breaker upon switch-on.

It won't. Those breakers have a current-time dependance to allow certain overloading for certain time. For immediate tripping a C 16A breaker it takes anywhere between 80-160A

https://www1.elfa.se/data1/wwwroot/assets/datasheets/f00407en-00_eng_tds.pdf pages 17+

On 230V it should be OK.
Compensated ballast draw lower current with cold lamp (les arc drop mean lower real power, while the inductive is by the large extend compensated).

To be sure, you can use 10Ohm/10W wire wound resistor (best with a thermal cut out, or worst case 2A slow acting fuse) in series with the input, bypassed by a relay (the relay should be supplied from the fixture input, behind the switch; the turn-On delay would be sufficient) as a soft start. That will limit the inrush current below 25A and that should be with great margin fine even for a 10A breaker.


On 120V with a CWA, when the breaker is accessible, you should work as well - the CWA does not have such high inrush current...
But the circuit breaker can trip when the lamp does not start for some minute (e.g. hot restrike,...), therefore the breaker should be accessible to allow to re-arm it.


All that expect no other significant load on that breaker...

@Ash: It is not a good idea to overload the breaker more than factor of two.
The electromagnetic trigger (fast acting, mainly designed to handle short circuits, but responding to e.g. charging the higher value PF capacitor) could be set to 5x rated current (for "B" characteristic; for "C" it is 10x), while you should not go closer than 50% to give some room for tolerances.