I had a great collection of toy guns as a kid. They are now classified as "Realistic Imitation Firearms". Still legal to own, but illegal to sell or import. And you can be arrested and charged with firearms offences if you have one outside of your own property boundaries.
Bizarrely, it's easier to get hold of a deactivated real firearm or even a working air rifle than a toy gun.
A school friend of mine had an awesome deactivated German WW2 machine gun. I've always wanted one but they are very expensive nowadays.