Hi Fee, here is the recipe I use for steamed jam sponge, its a Bero recipe and is as good as any I think.
100g or 4oz margerine
100g or 4oz castor sugar
2 med eggs
225g or 8oz self raising flour
2x15ml or 2 tblsp milk.
Jam or syrup
Grease a 2 pint pudding basin and put jam in the bottom.
Cream marg & sugar, beat eggs in one at a time with a little flour.
Fold in remaining flour and milk And place in basin on top of the jam.
Cover with pleated greaseproof paper or foil and steam for 1 and a half hours.
I hava an electric steamer that I use or you can use a pan but put an upside down plate in the bottom of the pan before you put in the basin, just so the basin doesn't touch the bottom of the pan, and keep the pan topped up with boiling water throughout the cooking time.
Hope this helps, happy baking! Gill.