on the flip side be careful your not over gunned with a carp rod,ideally you want a rod that's firm but forgiving in the fight,if the weed and snags are excessive go to even 12lb with a decent hook-length material,if you get run into a snag let the tension off the line slightly and wait the fish should come out itself you can then carry on playing it,and hopefully land it,70 cms is a really substantial fish that's almost 2 & a half foot in old money,the hook "snapping out of the fish" sounds rather damaging but hopefully it just threw the hook and no mouth damage occurred,i dont fish for barbel with main less than 15lb mono and my other reel has 20lb smoke grey braid its as thin as 6lb mono though.good luck with your monster fish,look forward to seeing the pics in the gallery soon
cheers
kev.