5w-20 or 5w-30 at a reasonable price, other than Halfords on TC (which I have)? Even with TC it is going to be pricey from them.
If this is for the Mundano, you need more info than that. It will take a low SAPS oil, so you're looking at also the C number.
If it takes the specific Ford specification oil (Ford spec oils start MC) that my Jag does, you're in for a bumpy ride, hopefully yours may take the older, low spec which is more common. I had to go to Opie (who, incidentally also offered the wrong spec based on reg) in the end to get anything at a reasonable price
Check the glovebox manual for the exact spec, as the likes of ECP do NOT offer the right oil by registration in my experience.
As AP are part of the ECP group, they too may offer incorrect oil.