^^ Any MKIV part that Chris Wilson makes or stands behind is going to be top notch. I don't know this "F1" intercooler by name but I do know of the dimensionally accurate all aluminum OEM style SMIC replacement that Garage Whifbitz sells in the UK for MKIV's... which, someone correct me if I'm wrong on this, should be a Chris Wilson design. It's supposed to flow a bit more than the original IC core as well.
As for MKIV heater cores, I know that The Brass Works in the U.S. makes them in LHD but they only copied that design, not the mirror image for RHD MKIVs. Although if anyone were to send them a worn out MKIV RHD heater core they could copy and remake it as well. The added shipping and wait time for may or may not make it worth it for RHD owners outside the U.S.
As far as I am aware they can and will copy or re-core any brass heater core design (or vintage radiator) that is presented to them.
This is the place I will go to when I need a stock SC heater core remade as well.