From the style of the box I would say that they probably date from the 1960s or 70s. However they are not fish knives and forks - they are dessert knives and forks and I can only see 6 of each in the box. You don’t mention what metal they are made of and your picture is not clear enough but you can buy a set of 8 stainless steel knives and forks on Ebay for less than £11.
Hi, thank you for your reply. (Feeling a bit silly now)