Hi would anyone be able to help with these hallmarks please, they are on the back of yhe knife but cant seem to see anything on the fork.
That’s not a hallmark - only U.K. sterling silver gets a true hallmark. This is a maker’s mark on silver plate. I haven’t found SN&Co yet, but the final S almost certainly refers to Sheffield.
ETA: The only place it turns up is on this page of unidentified maker’s marks: