Not backyard blitz but another now defunct show, my younger brother used to head up a crew that went in afterwards on some jobs and redid some of the work as it was shall we say “not up to standard”. He reckoned it was the biggest nightmare work around like coming in after a pack of no-idea DIYers had let loose. But it’s usually in a really good cause so it’s all good stuff, better than lining some millioniares pockets with TV revenue.
Keep an eye on them TB, I wouldn’t trust those TV types, they may need a rotary hoe, or spare concrete mixer engine or the annoying bloke may need a more powerful “personal pleasuring device” and we both know what they’ll use…. 
Bruce