Silver-
I worked for 44 years until I retired. At no time did I ever join a union, even when one was available. I cannot believe I am the only person in the country never to have joined so no, you cannot lump me and other non members in with unionists as 'working public'. Unions are, as far as I am aware, 100% left wing. If they are not I'm sure you will provide a link to prove otherwise.
Perhaps if you had joined a union, you might today be tens of thousands of pounds richer.
Secondly, you misunderstand how unions help the working public.
It is not simply a matter of directly helping their members negotiate better terms under their particular employers. By helping members fight for a better wage and better rights at work, they are, by implication, helping ALL paid workers everywhere.
That is the nature of Capitalism. In the same way that if employers are allowed to get away with paying below a minimum wage, they avoid paying workers a legal wage and find workers willing to pay a poverty wage, if employees manage to fight for better pay and conditions, then the standard for rises everywhere.
Besides which, union are responsible for:
etc. etc.
So, yes, you have benefited from unions, if you are a paid worker. And yes, you are mistaken. They're not "100% left-wing" - whatever that means. They benefit all members of the working public.