1. Cabana is gone and as no one will even admit they made it, the chances of it coming back are minute.
2. Willy Wonka is a fictional character. Most chocolate companies are multi-nationals who exist to make money and if building on a popular brand such as Dairy Milk will help them do that, they will.
3. Yes, some British manufacturers don't use the level of cocoa solids European manufacturers do. If you want more cocoa solids, several brands offer chocolate with 30% +. Buy that.
4. Nestle have made a terrible hash of former Rowntree bars by cutting production costs, but as Rowntree were bought out in 1991 and even the original factory is going, they're not going to be magically resurrected. However, Nestle are rumoured to be considering selling the confectionery side of their business, so from that point of view we may get better Lion Bars/Toffee Crisps etc. at some point in the future.
5. Chocolate, like most things, costs more than it did 20 years ago.
There we go - I'm sure there will be no comeback on this subject whatsoever.