Just had a look and the pricing has put me off too. I try to the one in Italy or maybe Retro Ronde, it's not far from Suffolk.
It is only about 50 miles to Harwich, get the ferry to hook of Holland and cycle another 130miles to the event sounds like fun to me. I could fit a beam mounted rack for the week end and take it off for the ride. I think I would get the train back. Entry fee is 30 euro's that is more reasonable.
I am also going to enter the 2014 tour de Flander sportive. 30 euro's too! I am not going to do another U.K sportive well I have only done one the ride 100 and I will make an exception for that again. All the other's are overpriced wastes of money.