The build

Quite agree, it may seem over the top but better do it properly first time round   . They always say the foundations is the unknown element of the build because you never know what you’re going to find . 
This part of the build is costing more & taking longer than expected    . 
Our guesstimate of the gravel we’d need wasn’t even close!! We’re looking at about 1000 ton by time we’ve finished!!
And it’s taking a lot longer because the quarry only has 2 drivers for all the jobs on the island. We’ve not had any gravel deliveries yet this week   .

You sound like you had fun with your extension! It’s all quite scary isn’t it!