I had a quick go at making up new channels for the door seals and it looks like one of those things that actually is going to be more of a pain in the backside than first thought:
The fold in the corners on the parts on the doors is more rounded (instead of an acute fold as shown in the picture above)
I think it is time to break out the special money hammer from the tool box and use that to buy some pre-made bits. There is nothing more irritating than door seals that fall off doors because they are not held in place properly...
...I hope the (blinking expensive) channels turn out to be better than my attempt other wise they'll be sent back!