I've been using JRC's leadcore leaders for a while now... and I think they're great!
Perfect set-up for your helicopter rig, the 45lb JRC Camouflage leadcore has a spliced loop at the top end for attaching to your mainline, and a quick change clip at the other for your lead. Just above this is the Heli-Gripter bead and rig swivel for attaching your hooklink.
I always feel confident I've got no nasty tangles after a cast, and know that safety wise, if a carp does snag me it won't end up tethered. The heavy lead core hugs the bottom well, so won't spook wary carp.
They retail between £3 - £3.50 a rig. For more info on all JRC products go to www.jrc-fishing.co.uk