That's a really nice find. This is a Tourist series bike (Model 1 "Popular", 2 "Tourist", or 3 "Superbe Tourist"). Those bikes would be the 28 inch wheel frames with the bolt-up seat stays and high bottom bracket with longer cranks. This series of bikes could be ordered with a number of "upgrades", and the extra equipment usually denoted whether it was a DL1, DL2, or DL3. The DL3 was the most deluxe; the DL2 middle; and DL1 lowest. The most deluxe bikes had FG four-speed hubs with Dynos; dry battery unit; mud flap at the bottom of front fender; full chain case; lights; pump; and bag. You could find any combination of these features, depending on where in the "Tourist" line your bike fell. These bikes had round-profile, smooth fenders. The more deluxe bikes tend to appear in "Suprebe Green" (like this bike) whereas the DL1 and DL2 tended to appear in plain black. I think yours is a Model 3 Superbe Tourist, but in a smaller frame configuration that was not seen in all markets, as the catalogs vary in whether they list the presence of that frame size.
Interestingly, some catalogs show only a large "24 inch frame" men's model, while others show a 22 inch frame. The catalog page above shows only the large size, but your bike is the smaller size. Perhaps the smaller size was only available in some markets (the Irish catalog has it, and apparently some came to the U.S. as well).
The Dawn series is a different bike. The Dawn is a rod brake version of the 26 inch wheel Raleigh Sports. The Dawn series frames generally have braze-up seat stays; lower bottom bracket; and the rain gutter Sports-type fenders. The frame angle is tighter than the Tourist series.
Determining the year of the bike is really a matter of looking at the features and hub imprints. The rear hub should have a date. 1950s on this bike is certainly a possibility. Going by frame serial number is tougher. I date the bikes usually by features; decals; and hub dates.
You'll have to keep an eye on eBay for a front fender, and may have to pay shipping to get one from England. The early, Superbe Green fenders from the 1960s and earlier in this size are hard to find in the U.S. The vast majority of rod brake roadsters in the U.S. today are black, plainer Raleigh DL1 models from the late 1960s through early 1980s.