Anyone who has access to market depth on the interbank forex market can see who the big players are, i.e banks etc. I subscribed to it on esignal and FXCM are major players. They are continually buying and selling, based, I would assume, on their customers buying patterns.
Make sure that there being present there is not based on availability of feed. i.e is eSignal listing all the banks worldwide or just a selection who make their quotes freely/cheaply available?. FX volume is almost totally dominated by a handful of players e.g DB, CITI etc not the retail brokers it seems eSignal carries whose volume is pretty meaningless. That feed probably be would be useful if you had the opportunity to scalp between them and had CIT DB's etc feed. As for their buying and selling, I make no actual or implied allegation regarding any of the FX brokers listed but as a general suggestion, in a best case scenario a retail broker is indeed laying off customer trades, in a [absolute theoretical] worst case scenario as he may be running a paper book and thus has redundant margin money lying around could be punting your funds in the market.