There are many problems with spelling competitions, several of which you point out. One not mentioned concerns the choice of words.
For a high-status national competition most words are probably fair game, though some neologisms (ginormous?) or not entirely assimilated foreign words may not be. There are also some words that have valid alternative spellings and should be avoided unless any correct version is accepted. One example of this is the word jewelleryjewelry (both spellings are given in the Shorter Oxford Dictionary). This is wrongly included in your list of common spelling mistakes and was incidentally also unwisely used in the recent national spelling test on ITV. I was also surprised that your list of common errors did not include the likes of "their", which many people find far more difficult than words two or three times as long.
Another quirk of Hard Spell was its attitude towards capital letters.
Competitors were apparently not required to indicate when a letter should be a capital, which purists might not accept as good practice (there is, for example, some difference between a "Nice biscuit" and a "nice biscuit"). Equally questionable was that all corrections were shown with an initial capital, whether proper noun or not.
Dealing with the competitive aspect of spelling competitions is difficult.
I was horrified at the way that those failing to "make the cut" were simply plunged into darkness as they stood there. Maybe they did feel like hiding away at that point, but I am not sure this was the most sensitive way of doing things. If there should be a repeat of Hard Spell it is to be hoped that some lessons will have been learnedlearnt by organisers as well as competitors.
Dr Alan Manford. 1 Parkside Road, Birmingham.