I have tried several mainlines both mono and braid but the one I always go back to is Power Pro braid in 20 lb BS, its not the cheapest line but for all round performance and abrasion resistance I think its pretty hard to beat. I use 20lb because I use the same reels for both carp and barbel fishing and also use this line on my multiplier reel for lure fishing. I usually replace my mainline every other season and have just done so recently. I managed to aquire a 1500 yrd spool from US on ebay for £85 including postage and customs charges, This is a saving of about £20 on uk prices. It tookabout two weeks to arrive.

Regards
Paul