In that case then most air weapons under 12lbs could be classed as "toys" you can get "brittle" amunination for anything, it will always be a grey area and will never be cleared up. The top and bottom is the police will if you abuse it charge you for a firearms offence, but if you average joe that paintballs proply you wont have much probem, eg a 17year old kid goes to the park and starts shooting dogs or people ... well there going to get locked up its as simple as that. Mr Average 35 year old goes to a reconised paintball field and has a mask, safety equiptment etc etc will be fine (under normall sucumstances). Grey areas are usually there on purpose so then they can decide if your a bad lad you get done if ya a nice boy your fine. To say "they break" is probly wrong as lots of full bore guns purposley "break" on impact usually to chop up someones guts and inflict max damage as apose to just go straight threw, the british army standard "accepted" 5.56 is designed for this purpose where as say a 7.62 (soviet standard round) isnt. My guess is play nicelly, play safe and your fine, and if for whatever reason they still pull you, plead ignorant and just take a slapped wrist or a caution lol!
I myself have firearms and shotguns, there is constant talk of "they will ban it" etc etc but the main fact is loads of these mps / lords shoot, so there never going to do that. I think people worry to much about not worrying, and then thats when any "anti" would jump at the chance, i can garantee there are "anti" paintballers who say it promotes the use of "guns" or voilence etc.
Moral of the story DONT WORRY TILL IT HAPPENS!
Chris