Celtic gold stater 'Whadden Chase' type 5.95g, 17.68 mm
The Whaddon Chase stater (yes, it is that type) will be CCI 05.0680. These coins are probably not very much earlier than the Addedomaros staters - it all depends really on when one dates the Addedomaros issue. It seems fairly certain that the Whaddon Chase staters could be from the later stages of the Gallic War, say about 54 BC at the earliest; they could be a little bit later, but are unlikely to be after say 40 BC at the very latest. If Addedomaros's spiral staters are his latest stater issues, then they could be somewhere around 30-25 BC, so perhaps up to 25 years later than Whaddon Chase. It just depends where each type fits, and we don't have an exact idea. I suppose it's true to say though that there is almost certainly a minimum of ten years between them, and more likely 20.
One of my colleagues recently suggested that the WC staters were issued by Cassivellaunus, to pay off Caesar during the Gallic War. They certainly seem to be found mostly in the territory of the Catuvellauni (so this one would be a bit further east than usual . The main catalogue reference for this type is VA 1476 in Van Arsdell's 'Celtic Coinage of Britain'. They're relatively common (300 or so recorded) but a lot of these are finds from the original WC hoard, found in Bucks in 1849.