The Marmalade Pudding cake (Kitchen) sounds and looks lovely, aside from the fact that I don't like marmalade. Can I use jam instead and adapt the sugar content so it's not too sweet?
Unfortunately we wouldn't suggest using jam instead of marmalade as it will dull the orange flavour from the orange zest and juice plus reducing the sugar quantity can affect the texture and structure of the cake. Also we suspect that the fruit in the jam (which tends to be party pureed as it is cooked until soft) could affect the texture of the cake as well.
If you aren't keen on the orange rind in marmalade then you could always try using a shredless (orange jelly) type of marmalade which doesn't have the "bits" in it and is a little sweeter than traditional marmalade. Several UK supermarkets have own-label versions of this or you could look out for the Robertson's brand. If you don't mind a little peel then the Tiptree "Crystal" marmalade is very finely cut and would also be good to use.