1. The two bolts holding cistern to pan won't come with a kit. Use
Screwfix 291HT.
2. The rubber coupling which sits between cistern and pan is called a "doughnut". Take the old one to a plumber's merchants and get an identical one, or as close as possible.
3. The screws to hold the cistern to the wall - work out the length and get appropriate brass or stainless steel screws if you ever want to take them out again. Also get soft washers, to fit between screw head and inside of cistern wall. Use tap washers or something like
Screwfix 599FY, or nylon washers. Don't do the screws up too tight or you may crack the cistern.
4. If you don't move the pan, the waste pipe should be OK.