Going to give this a go. Thanks OP
If anyones looking for the release valve ebay's full of them;
http://m.ebay.com/sch/i.html?_nkw=Twin+Bubble+Air-Lock+release&isNewKw=1&isRefine=true&mfs=GOCLK&acimp=0&_trksid=undefined.TR0.TRC0.Xtwin+bubble+air-lock+release&sqp=twin+bubble+air-lock+release