Hi, upfront, in all honesty I must admit, I personally think this is a shitty bike...
Heavy and ugly.
Still thought I could help to identify at least the year. Typically it's easy by identifying some Shimano components.
I have to give up. I've browsed through a lot of shitty Tourney rear derailleur to find that the RD-TX50 model looks like the one at the Wheeler.
E.g.
Daten: 400g Gewicht / 6/7 fach / bis zu 21 Gänge
ex-technik.de
Or
But even Shimano might not love those cheap groups a lot because there is no documentation or information about the year available.
Just my unconfirmed guess, it's might be a early 2000s year, so not vintage but rather retro design.