Anyone got any advice on what are the best conditions to train in to improve ones overall speed? Do you paddle in flat water, small chop or ocean to get the best benefits?

Cheers..

Train in at all to become the best all-round paddler you can be.

general fitness , technique , then specific training to the type of race you want to do well in. Train in all types of conditions. A big mistake people make in fitness is training in a way that has no or little correlation in the activity they wish to excel in.

Have a look at Larry Cains blog & training program.
Or there's Mic De Betta ( I'm sure the spelling is wrong )

Thought as much, just hard to tell if you are improving when paddling in chop.

That Larry Cains is a machine..

Stating the obvious but don't forget mental preparation! Need to stay focused and strong mentally during long races. Same goes to follow a training plan during winter ( my current battle??).