Thanks guys.
Unfortunately, raking isn't an option and particles are banned, but I will try putting out loads of small pellet to see if that encourages the fish to clear some space.
Halibut pop-ups sound like they are worth a try too.
I expect the fish will root around and find a bait buried in the reed stems, but fishing fairly stiff rigs, I doubt they are presenting well. I'm going to experiment with various lengths of supple braid and see how that works. I hear what you say about soft braid and helecopter rigs, but I'll try it out before switching to a more traditional rig.
Would a PVA mesh bag on the hook sink into the debris (I'm resisting the C word)? I always thought they helped slow down the hook after the lead hits.
Thanks, Paul