Okay, we've figured out it has something to do with your domain being an unusual format, "sweetsensations.uk.com" rather than the more typical "sweetsensations.co.uk" or "sweetsensations.com". That's confounding the routine we use to set a cookie in the buyer's browser to keep track of their cart contents, since cookies need to be set for a specific domain and in a way that can't leave them open to being read by other domains.
We're now trying to figure out the best way we could accommodate domains such as yours, but meanwhile you can get your cart functional right away by adding this to your View Cart code on every page, just before the "// -->" line in the standard code you obtained from Seller Admin:
function EJEJC_config() {
EJEJC_CDOMAIN="sweetsensations.uk.com";
}