two questions on a 1995 wrx

have a nardi steering wheel and want to change it , will i need to buy a boss kit or can i use the one from the nardi wheel ??

i want to decat my centre section , after looking around (cough ebay) there seems to be different bore sizes how do i know what size i need , i believe it is standard all the way through apart from the back box
and can anyone recommend were to get one (leicester area )

thanks phil