I eat them all the time as a HEX as they dont contain anything but cheddar and Marmite (not other additives/sugars/flavourings etc) and Marmite is free.
1 and a half Marmite bites works out at one HEXB or they are 4 syns each. They're not officially listed as a HEXB so it's up to you, but I cant see why they wouldn't be as they're just cheddar, they dont contain any more calories than normal cheddar so you should get 28g as a HEX.