Nice Webley, Richard! As you likely already know (and as already alluded to in this thread) the .380 service revolver cartridge was really a British military version of the .38 Smiith and Wesson (... i.e.
not the .38 Special ...) so regular commercially loaded .38S&W ammo can be used, and reloading dies are easily obtained. One note, however: the British loading originally used a 200gr. lead bullet (later changed to a 178gr jacketed bullet because it was felt that the non-jacketed pill offended the Hague Convention restriction on expanding bullets) with the result that the much lighter projectiles found in over-the-counter .38S&W will print very low ...
Also, while not wanting to rain on your understandably joyful parade, I perhaps should mention that the Webley .380 MKIV revolver (such as you have acquired)
wasn't the UK's primary-issue handgun in WWII - that honour is held by the Enfield .380 No. 2 revolver (Marks I and I*) ....
The Enfield is quite similar in over-all appearance and even in mechanical design (indeed, one school of thought contends that the designers at Royal Small Arms Factory Enfield simply "ripped off" most of their design from the Webley MkIV) but there are definitely significant differences, and parts do not interchange ....
Here is a side-by-side comparison of the Webley MkIV .380 (bottom) with the Enfield No. 2 MkI (by the way, the MKI* was the commonly-seen later version with no hammer spur, so that it could only be fired double-action):
On the bright side, during the dark days of WWII, the UK
did contract with Webley for MkIV revolvers, to supplement supplies, so the model is a British service revolver, albeit secondary issue ... Just think, however - this simply gives you an excuse to keep looking ... to add a .380
Enfield to your collection (and also at least one good .455 Webley, so that you have a NCOWS-legal British top-break revolver ....