I haven’t made them myself but here’s the recipe I have :
FLAPJACKS
4oz Margarine
4 level tablespoons golden syrup
3 oz granulated sugar
8 oz rolled oats
¼ level teaspoon salt
Grease a square, shallow tin, about 71/2 inches.  Put margarine and syrup in a pan and leave over a low heat until margarine has melted.  Remove from heat and add sugar, oats and salt.  Mix thoroughly.
Turn mixture into prepared tin and cook in a very moderate oven (335’F, Gas mark 3) for 30-40 minutes until golden brown (this actually seems a bit long to me).
Leave to cool in tin for 5 minutes then cut into 12 bars - it’s a good idea to cut them whilst they’re still warm because they get crisper as they get colder and if you wait until they are completely cold they’ll just break into small pieces.
Let me know how you get on !
Jo