The odds will always be in their favour and by not listing loaned to west ham - that's exactly where they cash in. Look at the two odds 8/1 & 1/4 - meaning if those were the only two outcomes then everybody could make a profit.
One thing I've learnt from betting against a bookmaker is that if something looks too good to be true - then it probably is. Betfair exchange has some markets to capitalise on though, if that's your game.
Just seen on skybet jenkinson is 1/4 to sign for us ( loans do not count ) . 8/1 to stay at Arsenal ! Does that mean if he is loaned to us he has actually stayed at Arsenal and they would therefore payout at 8/1 ?