Hi, any idea how to bring this old oak door back to life again..for example should I use varnish or oil after sanding .... 1920's how in a conservation area so I need to keep the door
I'd be very careful about sanding this. Have you thought about how you'll sand around the hinges, not to mention the bolts and not have the scratches show up? Particularly if you're going to oil this cross-grain scratches will be plainly evident.
I would try a stripper, then use scraping to get any tricky spots.
Make sure you oil it well where the ironmongery touches it - you'll have blue black stains everywhere otherwise. If you're painting the hinges do the backs as well, bare steel and oak are a no no. (unless you're doing it deliberately of course ) For the same reason don't be tempted to use wire wool.
Steel and oak are not good bedfellows so a good long lasting finish on the steel is as important as that on the oak. I would Galvafroid any bare steel before painting it.