I do have my doubts about show offers. We have asked for these and did get two almost identical quotes from two dealers for the same model, later we went to a dealer who was not at the show and their deal was only £50 different. It is probably worthwhile if you are looking for a specific model to see what you can get before you go to see if the offers stack up.
Many show deals turn sour where the dealer is many miles away and only interested in shifting stock. When problems arise you can then have serious trouble sorting things out which makes any saving pretty useless.
If you bargain hared though you will usually get a basic motormover or something else in the deal.