Whisk together the poppy seeds, orange zest and juice, vinegar and oils with some black pepper and a pinch of salt - be sparing with the salt, as smoked salmon is naturally quite salty.
Carefully separate the slices of salmon, then put into a mixing bowl with most of the radishes and spring onions. Drizzle over the dressing and gently toss together lightly - using your hands is best. Let the salmon marinate for just 5-10 mins while you toast the bread - any longer and the vinegar will begin to 'cook' the fish.
Spread the salmon over a large plate or platter, pour over any dressing left in the bowl, then scatter over the reserved radishes and spring onions. Bring to the table with toasted bread and a few forks, and let everyone help themselves.