The ironic thing is I found 3 rear bumpers hidden under a load of carpets in one of the two cars, about an hour after I put in a high bid on a bent MkI one on eBay.
So now, needing 2, I have 1 straight one, 2 slightly bent ones, and most probably another bent one when the bidding stops. But at least this will establish beyond all reasonable doubt, if the rear bumper is indeed a Mk I Ford Cortina front bumper.
There is a place in Folkestone, CE Design, who renovate chrome bumpers, so I will take all mine "in need of" down to them, and I should have 3 good rear ones spare at the end.