Once again I have the greatest of pleasures in correcting you Gareth.
For your info the fore sight that you have may be an original FWB Sports one. Its the type that completely surrounds the barrel (i.e. Webley Vulcan) and is held in place with a cross bolt/pin. There is a corresponding groove in the barrel to facilitate this.
RAYGUN and I both have FWB Sports which are standard from the factory, no barrel shortening and standard length and both these rifles have the foresight units mentioned above. Ive also seen it (rarely) on other 'Sports including the one in the 'Airguns On Test' annual 1980 page 40 (See here)
As you say E.D.A.S.D.
ATB
Ian