You'll want alloy rims. Pashley can source them.
Planet Bike Cascadia fenders are appropriate for DL-1 restoration.
A full chaincase can be bought off the UK eBay.
Schwalbe makes creme tires in the 40-635 size.
Forget hard to find rod brakes. I recommend drum brakes which provide reliable all weather stopping power and give the bike a cleaner look.
Nitto Albatross bars for the stately look. Grips are hard to find. If Hunt Wilde retailers or Harris Cyclery don't have them stocked, Brooks leather grips give a good "period" appearance to a DL-1.
All of which amounts to a considerable project. I'd recommend selling the frame and buying with the cash a Pashley Sovereign roadster. You'd get a bike that has everything you're looking for in a roadster.