Listen my young friend...as a person who knows one or two things regarding the law and firearms.
It is illegal for a FIREARM to be capable of Fully Auto Matic fire, as covered by section 5 of the Firearms Act.
It is illegal for any FIREARM, to be capable of Semi Automatic Fire, except for those in the 22LR Calibre.
Fire an AIRGUN, to be deemed as a FIREARM, it must be found to be producing more than 12Ftlbs of muzszle energy.
Also...I dont think that a paintball gun, is classified as firing a Lethal Projectile (as airguns are), and are therfore not classified at this time.
Further more, in the recent amendments, it clearly states that " guns used in Wargames and similar, that fire balls of paint, are not deemed to be lethal and therefore should not be considered as Firearms" or words to that effect.
So go buy stuff...I recommend Virtue.