I am looking at buying a water cooler for my rig but not sure if i need to. My FX-6100 CPU temp is running around 42c with the stock cooler when i'm encoding video which i think is hot but i dont know Can someone tell me please if this is ok or not and recommend a water cooler around the £60-80 mark for a Asrock extreme 3 970 MOBO
no need for water cooling. stock is performing well in your case.
42 degrees is quite normal. Even you don't need other air cooler. You should consider water cooling loops when temps will getting very high.