Bleed the system out as instructed in the Haynes manual. Basically this means pumping old fluid out of a bleed valve with the foot pedal whilst topping up the reservoir with new stuff.A one man kit like this makes things easy.

It took a whole night to replace these hoses. That was about 4 hours of fairly strenuous activity. Bleeding the system ranks as one of the most boring jobs going. It needs another go at bleeding as there is still a bit of sponge in the brakes, but not enough the prevent the wheels locking up when tested.