How do you make golden syrup?
In Britain golden syrup is used in a lot of things, Lyle's brand is the one people know, though there are a few other minor brands. They tend to vary in thickness and strength of taste, but usually have fairly similar tastes. It is partially inverted sugar syrup, which has a fairly complicated chemical process to manufacture from byproducts of the refining industry. I doubt it's very easy at all to make at home.

Buy a whole tin, it is quite versatile, excellent in cakes and best of all on porridge.

Quick tip: If you need to add a large amount to a recipe which asks you to heat it, which is quite common, it is far easier to place the tin (with the lid off!) in the oven for a few minutes and carefully wearing gloves pour from the tin, as the heat makes it thinner and thus pourable.  Same thing works for black treacle.