What world normally happen is that there would be new legislation which would repeal the 2009 Egg act, probably in the form of a section inserted into some other legislation which was going though at the time, legislation can usually only be amended via new legislation. If they wanted to do it as standalone legislation you would get the “Egg (amendment) act 2010”. Even though it has the word “amendment” in the title, it’s still new legislation in its own right, and must go through exactly the same process as all other new legislation.
In the case of firearms legislation it would be even more complicated, say that the government wanted to repeal the current gun laws, they could have legislation which just repealed the 1997 firearms (amendment) act, but there would still be other laws in force (the 1967 firearms act for instance). It would be much more simple, and legislatively easier, to say right, here is the Wild (north) West act 2010, which states that everybody must carry at least one six shooter in case they want to hail a cab in the Lake District.