I think the sheer volume of races in Britain is detrimental to their chances. Trainers have far more options with regards to where they run their horses compared to trainers in Ireland. This leads to British horses running in less competitive races throughout the year, resulting in a large number of inflated marks.
Irish trainers on the other hand have far less options available to them, forcing them to run their horses in more competitive affairs. This results in horses getting lenient marks for finishing down the field in high quality races. The Storyteller running in the Flogas being the perfect example. Mall Dini (I know he didn't win) running against Presenting Percy and Invitation Only another good example. Those runs should have been marked up purely because of the quality of the opposition.
The whole thing results in a large number of English horses running off inflated marks that they probably did not deserve, and a much smaller number of Irish horses running off high marks that only serves to hide the true ability of the horses that ran in behind them.
I think you raise some very good points with this and I think no horse advertises this better than Buveur D'Air in the Champion. I can't have Melon and Mick Jazz as close to him as they have actually ran on Tuesday and I think this comes down to the prep Buveur D'Air had. I am certain Nicky Henderson will change its racing program next year as I think they have got as close as they have due to the horse not having a serious racecourse blow out. Clearly the best horse in the field and it was not that far from getting turned over, even if some believe Melon to be very talented, I cant have Mick Jazz only 2L further back. I think they will almost certainly take in the Dublin festival on route next year, providing the horse is fit and well.