Old recipe.

Probably. My mother used to make pastry with half lard, half margarine but I use all marge and it comes out OK. Butter in the biscuits might be even better.

I would imagine it will work ok, probably a case of try it and see. I expect the biscuits would be crisper made with half lard in a similar way that shortcrust pastry is, but if you don't mind a softer texture no problem.
I buy lard from supermarket, always make my pastry half marg and half lard.

It'll be even nicer if you use butter. #LoveButter

I still use half lard and half Marg in my short crust pastry - comes out a treat .

Trex? Cookeen? They were staples of my mum's kitchen especially when baking.

I love butter, too! I made a sponge this morning with all butter, as I didn't have any marg. Actually I haven't baked for a while, and the sponge was a bit lop-sided and not terribly high, but that was probably because the flour was a bit elderly.

I remember Trex and Cookeen - my mother used Cookeen, as it was a bit cheaper than Trex!

My best shortcrust is made with all butter, though, in the past, I used half and half butter and white Flora which made a very light pastry. Is white Flora still available? I don't remember seeing it lately.