I would be carefull with these as they look very much like replica fire arms which can land you in a world of sh*t.
They are completely legal to own, as long as you are over 18 and their power is less than 330 Feet Per Second (might be 350, but most site limits have it as 330 or 328FPS).
To purchase a new airsoft gun classified as a "replica firearm" under the VCRA (Violent Crimes Reduction Act) generally speaking you
must be a member of the UK Airsoft something Association (UKARA).
Some guns are exempt though (for example, my 1873 Winchester replica is exempt as it is a replica of a pre-1900 weapon).
The other exemption is that if more than 50% of the gun is painted in a hivis colour, like flouro yellow or orange or red, it is no longer classified as a "replica firearm"; and so you see newbs running around at airsoft sites with pink guns and so on.
Of course you cannot take one out in public, it must be in a bag at all times, etc., etc.
As long as you're not stupid with them and you act within the law then there's no problem regarding ownership and playing the sport.