Put the cream, caster sugar and vanilla pod in a saucepan and heat until just below boiling point, stirring occasionally. Remove from the heat and leave to infuse for 20 minutes.
Meanwhile, heat the granulated sugar in the measurement water in a heavy-based saucepan until it has dissolved, then boil until the syrup turns to a golden caramel. Quickly pour into 4 x 150 ml (¼ pint) ramekins or small moulds. Set on a tray and leave to harden.
Pour the milk into a small saucepan and sprinkle on the gelatine. Warm over a low heat until the gelatine dissolves. Stir into the infused cream mixture. Bring to the boil, then immediately remove from the heat and strain through a sieve into a jug. Pour into the ramekins or moulds. Leave to cool, then for at least 5 hours, until set.
Put the apricots in a small saucepan with the measurement water, sugar and vanilla pod. Bring slowly to the boil, then cover and simmer gently for 5–8 minutes until just tender. Leave to cool, then remove the vanilla pod, cover and chill.
Carefully loosen the panna cottas and turn out on to individual serving plates. Serve with the apricots.