In almost all aspects the National Lottery would be perfect - its all online, direct debit, auto plays the tickets etc, well established.
But, the prize pool being only c.50% of the ticket price really puts me off. Its not just good causes according to wikipedia, there is a 12% government take as well.
Maybe a jackpot slot is the way to go, will just need more effort each month for us to log in with our allocated cash and do the spins. Also Im gubbed from almost all bookies from my matched betting days. Would have to be much more discipline involved if doing the jackpot slot route, it would have to be treated like a lottery ticket - play the allocated amount and stop regardless of win or lose.