Hmmm, erm and any other letters to signify desperate pondering....lol
So what do we get for the 549.99 gbp? So it's a shopping cart. But; is it? You built it and it didn't take off. Does that mean it doesn't work? Maybe it means that it is too difficult for users to buy through it and so they didn't? What makes your shopping cart special when compared with any other that we can get for free but which comes with paid support? Does this cart come with paid support included?
I expect you have devoted some considerable time to the project and I don't mean to sound harsh or take away from that effort. But I am struggling to find value of that magnitude.