it's different when it's loose items in store like cauliflowers.. this was a prepackaged thing and should have been properly cleaned. also, the salad contained non-plant items like tuna and boiled egg. blood in steak doesn't really pose a threat if consumed, but a maggot could.
anyway, they gave me a double refund rounded up to £8 and have sent it off to a lab for analysis, to find out a) what it is and b) if it poses any risk to health.