Place redcurrants and blackcurrants in saucepan with sugar, and heat for 4-5mins until fruit is soft but retains shape, and there's plenty of syrup. Add raspberries and blackberries, stir well and heat gently for 2mins. Leave fruit to cool, adjusting sweetness with little more sugar if nec. Set aside 100ml of fruit and syrup, cover and chill.
Line 1.8litre pudding basin with bread; place piece on base, 4 around sides, and fill in triangular gaps as neatly as poss, pressing edges of bread together to seal it. Tip fruit into basin and press down. Make lid with more bread. Place plate slightly smaller than diameter of pudding basin over top and place weight on it. Chill overnight.
Run palatte knife around edge of pudding to loosen it and then invert onto plate. Leave to stand for 30mins, to bring it up to room temperature and to allow juices to soak into base. Spoon reserved fruit and juices over top, soaking any bits of bread not turned red. Serve with clotted cream.