So you dont like the external hinges, or they are just worn out?
or maybe you want to meet the SVA specs on your build, here's how.
This is the hidden hinge kit, available from Rocky hinge.com and anglia-brokers.com
This diagram shows the basic idea of how the hinges fit into the A pillar.
Shown with the door closed, and the dimension to be aimed for.
Before you start, you need to tap the hinge for a 6mm thread in the position shown, this will be your adjustable door check, do this on both hinge straps for each door.
This shows how it works in principle, (bolt length exaggerated for clarity). Use a high grade Allen bolt with a locknut fitted, and adjust so both hinges take equal strain once the doors are final fitted on the car.
Start by making a clear surface to mark out on, I used a little primer painted on for easy drawing out.
Plan a good place for the hinges to go, 2" down from the original hinge pocket is about right.
Hold the hinge against the door post and mark around it, holding the pocket flush with the inside edge.
Keeping the lower pocket flush with the inside edge again, mark out the lower pocket cut-out also.
If you have a shelf bracket fitted, it will need to be removed, it can be welded back later if desired.
Inside edge of the jamb top, I set the hinge back to get the recess flush top and bottom. With the hinge in the closed position, check it is level, and move hinge to suit if not.
Some trimming of the pocket will be needed to get it flush with the door post.
The bottom hinge is 3/8" in from the edge, I then tack welded it in place.
Make sure it is all level before tacking in place!!
You should be aiming to keep the box section level with the A post edge, which should be 90 degrees to the bottom door edge. It's important to triple check this or your doors will open slightly upwards or downwards otherwise.
The vent can be welded to the hinge if you have these fitted.
Another view from the opposite side.
Once the hinge is tacked in place and you are satisfied that it is all level, you can start to mark out the doors. Place the doors back in the body and wedge them in the correct closed position, taking care to maintain even door gaps all round, and flush door fitting to body.
Mark around the hinge and also the hinge pocket.
The pocket will need to be a little longer in the door than the hinge, to allow for door adjustment.
Check to see how deep into the door the pocket needs to be recessed, this is important! and then trim the door carefully to suit.
My door had these measurements, but yours may be different!
You will then need to trim the pocket down to suit the length and depth of the hole.
The top hinge needed a set down of 1/2" into the door, the lower one only needed 3/8" set down.
When you are satisfied it is all in the correct place, (tack it together & check first!!) you can seam weld it all together. Its worth adding extra welds to the factory joins as well.
The lower hinge will need new steel to go in to fit. Fold a small return on the rear edge for rigidity, and weld in. again, adding extra welding to the factory seams for additional strength. This extra welding can be seen better in the photo below.

The body will need some additional bracing, as it was not designed with the twisting loads this hinge will place on it. On my car I added some steel tubes to carry it forward to the bulkhead frame, which goes across the car, you will need to construct some kind of a similar style frame to go in your own car.

With the door mounted back on the car, you can easily adjust for perfect shut lines.
When you have finished, you will need to fill in the original holes in the door skin & the body hinge pockets. Carefully make up some filler pieces to fit....
And weld them in. With some dressing of the welds and a skim of filler, the job will be complete.
And there you have it, the completed job. All it takes is a little patience and a lot of careful measuring, to get a smooth and SVA compliant hinge on your Anglia.
If you can weld, this is a very simple job to do.