According to the E.R.Shaw webpage, they currently retail at US$105 ea. I paid about $95 at the time. Not everybody likes Shaw barrels BTW, however these look fine to me. I haven't put a tool on them yet, so can't really comment. Hope they're OK! I'm sure there would be other manufacturers pricing competitively on your side of the pond.

Also the twist-rate is a little slick for 12-bore slugs, around 1:28 IIR, so probably designed for sabots. I'll be shooting 750gr Fosbery-style slugs for starters, if I ever work my way clear to getting this project underway!