Dislikedmost volume is traded by.....they make up over 70% of intraday vol....hedge funds borrow from these banks
1.deutsche bank
2.ubs
3.barclays
4.rbs
5.citi
6.jpm
7.citi
8.hsbc
9.goldman
10.credit suisseIgnored
Moreover banks are intermediaries, not players, for example if people want dollars to invest leveraged in stocks they lend them dollars and dollar fall against the rest of currencies, etc. The prices in currency pairs don't move exclusively by the Forex traders, that's the difference with the rest of markets, and banks are only intermediaries I repeat.
Edit: the only banks that take part in Forex market are Central Banks.