On the origin of bangers and mash, technically we got potatoes from Virginia in the late 1500's. Sausages, well they were around in 500 BC or so but I'm not sure we had them or not. The gravy we stole from the French in the middle ages.
Really about the only bloody things that are native to us is bread, dogs, oats and rabbits. I suppose we invented hot dogs although being British it would be "dog on toast"
Rabbits are a recent introduction, by the Normans. They were kept in purpose built warrens, for the (Norman) nobility.
They've been here a bit longer than that, it was the Romans that introduced them to Britain.
Hence the slang term "coney", the etymology of which derives from the Latin "cuniculus".
Make sure you spell that with one "n" or it ends up meaning something else...
Actually, since I was a kid, it seems it has become more difficult to foretell the past...
"The question of when rabbits (Oryctolagus cuniculus) first reappeared in Britain is somewhat more complicated. Rabbit remains have been found dating back to the warm climate of the Cromerian Interglacial (750,000 to 350,000 BP), suggesting rabbits were found in Britain before the ice sheets advanced. It seems that they didn’t, however, make their own way back to Britain after the ice retreated. Rather, it appears that Roman settlers may have been the first to bring rabbits back to Britain.
"In 2005, archaeologists excavating a Roman settlement at Lynford in Norfolk found the remains of a 2,000 year old rabbit dinner, which may represent the earliest evidence of rabbits in post-glacial Britain.
"Norman settlers subsequently brought rabbits to Britain with them and they are widely considered to be the origin of our current rabbit population. The precise date and source of the Norman introductions remain unclear, although the earliest definite mention of a rabbit warren appears to be from the Isles of Scilly in 1176."
https://www.wildlifeonline.me.uk/questions/answer/are-foxes-and-rabbits-native-to-britain