I have a Lappierre Zesty 314 (2012). I'm running xt rear mech, a slx front mech, and my crank is xt and rear cassette is xt and xt chain. I went to the forest of dean and after the day was over I snapped my chain! So I picked up a sram chain for my bike and now when I pedal hard it slips with a big bang. I have new eastern havens so my hub is fine. Can you help with any ideas to help me solve this? Shall I get a new rear cassette?
Look up the proper chain for the components. XT is not a size - that is the group level. You should size the chain for the number of speeds (gears).
Inspect the cassette. As they wear the teeth get sharper spaces get longer. Visually compare it to a new cassette even if you are looking at a picture.
If your chain snapped then possible something else is damaged. Inspect all the drive components.
A cassette typically last 2-3 chains. If you get a new cassette then change the chain.
A worn chain wears a cassette down faster.
A chain is cheaper and easier to change so cheaper to stay with a fresh chain.
A new chain on a worn cassette will jump - basically both the chain and cassette stretch.
Typically you'll want to change your chain and cassette together, since they will both be worn, so it's not surprising that you're experiencing some slipping. It's also possible that your existing cassette is bent or damaged in some way rather than just being worn. I had an old XT 9-speed cassette where I somehow bent a few teeth to the right in the middle range, and even though it was barely noticeable, it made those middle cogs totally useless under load.
I assume you also bought a new chain that's the appropriate width for your rear cassette (9, 10, 11-speed, whatever). So if it's adjusted well and you have the right chain, I think it's safe to say that you'd benefit from also replacing the cassette.
Chain slip, after replacing a chain, usually indicates worn cog(s) and/or chain-wheel. This can be avoided by replacing the chain early, before major wear has taken place. The snapped chain is problematic. The break could have been caused by an extremely worn chain. If the original chain had no master-link, it could be that the pin was not installed exactly as it should have been. This pin could have popped out on a well worn chain. If you still have the broken chain, re-install the chain, replacing the broken link with a quick-link (master-link). Now, does the old chain slip? (be careful during testing) If the old chain does not slip & the new chain slips, then you will need to replace the cassette in order to use the new chain. (one or more chain-wheels may need to be replaced also)