Here
http://www.bbc.co.uk/food/recipes/bolognese_sausage_rag_01151, he says use good quality coarse pork sausage meat. I really don't know what the difference would be between Italian sausage meat and English. I mean, if it is just coarse minced pork then what would the difference be?
The only difference would be in the seasonings added to the sausages (if you were using sausages rather than plain minced pork). I found this on Nigella's website:
I think the dish that Rick is making is a generic Italian recipe. There will be many variations, depending on regions and the type of sausages used. I would bet that if he cooked this dish in the UK he would use a different sausage and it would taste slightly different. And you could go to several Italian delis and find different 'Italian sausages' in the UK. So, whatever you do, the dish will never replicate the one that he cooked in the TV programme. Well, not exactly, anyway.