i think you would find that if the stakes are in the £5 + mark then people will put the odd £5 or £10 in if they have won elsewhere but i cannot see it creating a "hardened" player base due to the cost involved ..
how much would it cost to force the jackpot !!!!! or even 20 people all over the country trying to force the jackpot ... one wins it .... how full are the local bridges and rivers going to become after that !!