They have!! In 2008, 2009 & this year they ran a five day event through northern France/Normandy totalling around 350 miles each time (I did last year's ride). Each ride raised around £1 million for the charity!
This year, due to popular demand they are running another ride (in September) to Arnhem (again, around 350 miles over 5 days) - I'll be there!
I think they are still accepting registrations/applications but you need to raise just over £2k in sponsorship (half pays for the trip, the rest goes to H4H).
Or you could arrange and pay for a trip yourself, raise the same cash and give it all to charity.
A grand for 5 days? My two week tour this summer came in at less than a grand, and that was all hotels/B and B, and eating out in the evening, and included ferry fare, and lunchtime picnic kitty. I wonder how the organisers can spend a grand on each person over 5 days, even accounting for publicity, admin, insurance, back up and so on - bearing in mind they'll probably have economy of scale in terms of accommodation/food.
I suppose the charity is grateful for what they do get, and most people wouldn't get off their arses if it wasn't all sorted for them. But I'd be interested to know how much profit (if any) is made for the organisers.