I know this is known as a cheap and easy upgrade, but i've been having problems fitting mine

They're going on a MK3 2L hub, with vented discs, i've managed to get the discs on after removing the backplate, but the calipers hit the hub when in place, I know there needs to be a 5mm spacer on the caliper mounting lug ( which i have'nt got ) but it still does look like they'd fit!
Am i missing something? the calipers are from a 2.8i MK2 granada ( m16 type )
Would be grateful of any help,
Cheers,
steve