SA80's were on the Market in the 80's, Pat Walker guns had them (Advertised in Guns Review) , Although there are a few who don't like to see these adverts, I'm sure a few who have posted regarding the bayonets will testify to this. A few of the old adverts, the last one I love regarding the Sherman tanks........ I don't know what £10,000 in 86 would be worth now, but if anyone ever invents a time machine let me know.
https://www.milsurps.com/images/impo.../A0yFMtV-1.jpg
https://www.milsurps.com/images/impo.../vftT8Mn-1.jpg
https://www.milsurps.com/images/impo.../nhWVGhw-1.jpg
https://www.milsurps.com/images/impo.../KKs4hMZ-1.jpg