In the 70s gun crime was non-existant outside of big criminality in Scotland. As best as I would know, pretty much the whole of the UK,
Since about somewhere in the 1980s, there has definitely been more guns available, certainly in Scotland, Manchester, Bradford/Leeds, Liverpool (the latter 3 from TV, popular press etc). London, Birmingham, Im not sure about.
How much actual "crime" Im not sure. There were turf war reports of gun crime between rival gangs in Liverpool, Manchester and Bradford/Leeds that I remember about 2000-2001 or so. About 2 years ago there was a Police wowan shot in Bradford that made the national news constantly for a while.
In my city Edinburgh, there are on/off gang feuds between rival drug gangs with the odd pistol popping since at least 2005 (maybe further back - its not something I do a Phd study of), but it is still fairly small scale. Edinburgh is not a place that will tolerate armed crime and it dies down quite quickly. However in the 1970s, this just did not happen at all.
What there is not, is the wanten gun violence like the US, noticeable exceptions being Hungerford in 1987 and Dunblane in 1996.
As best as I understand, there is greater supply of guns into the UK, mostly coming from eastern european traffickers' capability and willingness to smuggle guns into the UK.
There was a report of folk in Glasgow about 3 years ago or so, of guys in sheds converting replica guns into zip gun single shot pistols.
Whether this translates into a greater desire to use guns in low-life street criminality, I have no idea.
Our culture is much more about getting drunk and fist/feet brawls outside clubs etc - this I see just about evrey time I am out on a saturday night after 12 pm, pretty much everywhere in the UK.