The MKII seat does have a clip to stow the centre lap belt tidily when not in use on top of the squab but it's impossible to train the kids to use it 
The buckles for the outer rear belts are again totally conventianal and are attached to webbing straps that fold down behind the bench and anchor to the bolts in a very similar way to the MKI although the MKII webbing straps are very much longer.
You are going to need a MKII lap belt and a set of MKII buckles to use the seats properly as the MKII bench will be lacking the cutouts that accommodate the centre inertia reel and buckles when they are not in use.
I never appreciated the significant difference until your post prompted me to take a look!
Another reason for my view that the MKI is a far better car in so many ways.