Just to confuse you further, some of the legislation has been changed to 18 other parts are still 17, have a look at the below, below shows the date when certain parts of the law changed 1st Oct hope it helps:-
Subsections 22(1), 22(1A), 22(4), 24(1) and 24(4) of the Firearms Act 1968 (as amended by the Anti-social Behaviour Act 2003 and the Violent Crime Reduction Act 2006) restrict the general acquisition of, possession and supply of firearms and ammunition by or to persons under seventeen years of age. They state:
22(1) Pre 1st October 2007
22(1) It is an offence for a person under