So is the UK going to go after gun sellers and makers as well?
Handguns aren't entirely illegal in the UK. If I'm not mistaken then, roughly speaking, what the law prohibits is rifles below a certain size. In the UK it is possible, for example, to legally own long-barrelled pistols and old flintlock pistols. Another caveat is that the ban doesn't apply in Northern Ireland.
I don't think this really detracts from your point at all.
The law mostly concerns itself with the length of the barrel, the firing mechanism, and the ammo cartridge size, as well as the ability to discharge noxious substances.