What to use on saddle clamp? I'm purchasing a new seat-post as my saddle refused to stay at the same angle with my current one; it was a second hand bike (B'Twin Triban 500) with a single bolt clamp. I'm going to switch to a two bolt clamp to try and fix the situation, and hopefully get the right angle! 

However, I can't find any information on whether to use grease or threadlock on the bolts. I use grease on most bolts, and don't actually have any threadlock; I believe I'd be looking to get Loctite Blue-243 or Blue-242 if I needed it? Furthermore, is there a difference between threadlock and anti-seize?

Thanks!
A very thin coating of grease will help prevent the threads corroding or sticking together, as will a specific anti-seize product. You definitely want something on the bolts as water and crud gets thrown up into the bottom of the saddle by the rear wheel.

You can use thread locker, but if you have been having trouble with the seat bolt coming loose you are probably not tightening it enough. You can try taking the bike to a repair shop and having them use a torque wrench to tighten the bolts properly.