Place the flour in a bowl, make a well in the centre and break in the egg. Gradually add the milk, mixing with a hand whisk to make a smooth thick batter. Season with salt and pepper and stir in the sweetcorn.
Heat the oil in a large frying pan, add spoonfuls of the batter and fry, in batches, for about 5 minutes, turning once, until golden and crisp. Drain on kitchen paper.
To make the salsa, place the tomatoes in a bowl and crush lightly with a fork. Add the spring onions, sugar and French dressing, season with salt and pepper and mix well.
Serve the fritters with the tomato salsa and guacamole.