I'm jumping way ahead from my place on page 4 (catching up), so apologies if someone has already addressed this.
I think the Masterchef gig is a perfect cover for the Hams 'getting the hell out of the UK Dodge' without any hullabaloo about why they're going (ie because the move to the UK has been a colossal failure on many fronts).
They go, bide their time a bit, and then during, or as soon as, filming wraps they announce how much they LUUURRRVVVE Aus, how the weather/the lifestyle/the people echo their 'beloved' California so they've decided to stay put.
They have the money to up sticks and leave relatively easily. They own no property in the UK, they have no real 'ties' there since the RF has said 'Thanks, but no thanks" so I think they figure there will be no help or money from that quarter. And it sounds as if any friendships they've made there are 'new friendships' and easily jettisoned. I'm not sure how similar the UK vs the Aus educational systems are, but I'd think it's more similar in nature to the UK than the US system. So I suppose it would still count as a 'British education'. Kinda.
I suppose the downside for Harry is that the Hamlets will end up with Aus accents rather than a UK accent. But the upside is that he can get back to the sand, surf, and sun life that he had in Montecito.
It also, I think, distances them a bit from the TMSr scandal. I think her 'involvement' (or lack thereof) is a much bigger media 'thing' in the UK than it is in the rest of the world.