Under the VCRA 2006 introduced to limit the sale of BB guns. Any gun, real or not, used to strike fear in someone for illegal ends will be deemed as a real gun when pressing charges. So it is irrelevant if you thought it was a real gun or not. It was used to help carry out an illegal act, under the law it has to be treated as the real deal.worst thing is the CID come over an asked "are you sure it was a real gun" they weren't taking it serious at all.
How do I know this? Because up until recently I took part in competitive air soft and to be able to buy new RIFs as the legislation request they are called, I had to buy a gun locker to keep them safe. TBH, it is easier to buy a real gun illegally than it is to buy a fake legally.