I have a question about putting down a second layer of loft insulation. The roll has an insulating foil - I guess I need to either remove it (could be very impractical) or cut it. Should I put this cut foil layer on top of the first layer (i.e. face down) or leave it face up. Does it make any difference?
Any advice would be great!!

Do not remove the foil layer; it helps prevent moisture ruining the insulation, and prevents wind penetrating the insulation.

You ought to have a condensation barrier (plastic sheet) below the first layer of insulation. So you can use the foil layer to prevent wind through your attic decreasing the efficiency of all the layers - that means lay it with foil upwards. If you haven't got a condensation barrier, your under layer will get damp and stop insulating.

Make sure you don't block the ventilation holes in the eaves.