If it's a Zetec engine you should use Zetec oil, available from Ford agents, although places like National Tyres or Kwikfit will use it provided you ask for it. Otherwise, you won't do any better than Mobil 1,
I have a 2ltr Zetec Modeo Auto (2000) and always get Kwikfit to do my oil and filter changes. Costs about �20-�23 so its hardly worth doing it yourself - and I have no comlaints about their service.
I understand your point, Toureman, but bulk buying is a lot cheaper than high street prices. I can buy 5 ltrs of Mobil 1 for about �12-�15 in Costco.
Spin-on oil filters for the Mondeo cost about �4. So I think the two companies I mentioned could still use the correct oil and make a profit. However, I always change the oil and filter every 6 months or 3,000 miles, whichever comes first.
Incidentally, your Castrol link did not list a product for the 2ltr Zetec Mondeo.
Halfords own brand range of engine oils is pretty good. Halfords don't make oil, or bikes or anything else. It's all re-brands of others. I know what the Halfords range is re-Branded from and it's definitely in the upper end of the spectrum.
IIRC, don't Zetec engines require a 5W-30 ? Sorry, been out of lubes for a little while and memory is going. Still remember what goes into my VAG 1.9TDi lump, though.