Jackpot Joy do still pay for "free" leads - if you've got a lead showing with no commission, then that means you've introduced a "real" player, who has deposited funds and will earn you a % of their losses. The commission for this is updated in a monthly batch, normally around the 25th/26th of the month.
what happens if a free player we introduce (and we earn the 50p lead on) later deposits money? if this is done within the cookie time do we then start earning a % of their losses?
When the free player registers, we store the affiliate's id in the member database upon creation.
That means that if the Free player chooses to play for real at any point in the future the commissions will come to you. (Even if you decide to stop promoting us between now and then).