Hiya, I do AQA triple science so I can only help you out with a few things but here goes
Revision guides are very helpful for extra information that is not necessarily in a school guide.
In my opinion the CGP guides are very good. They are funny, presented in a good way, and cover basic as well as more in depth information than the (in my case) AQA book covers. They are thicker with more space for diagrams e.t.c.
Most book stores sell a huge variety of revision guides so if you go and check them out you might find one you prefer. Waterstones, amazon, wh smiths e.t.c
If it's the same as aqa then triple science includes (P1,P2,P3) (C1,C2,C3)(B1,B2,B3) with the unit 3 being the extra triple science bit.
Bitesize is good, there are also lots of good youtube videos(just search it).
I'm currently on target to achieve an A* in all 3 sciences but we'll see how it goes.
As for past papers go onto the edexcel websites and there should be papers and mark schemes on there.
Hope this helps.