Matching old architraves can be a pain. Friday was my last day on working on the old rectory until next year and one of the final jobs I did was to make up some architrave.
I did this by ripping down some MDF and putting a bead on it with my little router and fixing this to the frame. I then went to fix on some normal architrave on top of this but it looked far to big, so it was back outside in the cold to rip down the architrave until it was the same size as the other. All glued and nailed it matches in well (I also put in the blocks at the bottom of the architrave like the rest of the house), just needs a coat of MDF sealer and a lick of paint.