I don't whether something is terrorism as something that's relevant for whether it's allowed by the laws of war.

Instead what we have is IHL, i.e. the Geneva and Hague conventions etc., and if you are targeting military personnel or other targets of military importance, without any extra cruelty or attacks on civilians, what does it matter if it looks like terror-bombing?

If it's allowed by IHL but is terrorism by British or French of German law or whatever, it's allowed. IHL is the actual binding thing.