Trial pits (and water features)

So to suss out our ground conditions we dug (and dug and dug) a trial pit.
We found thick, heavy sticky clay & managed a trial hole about 70cm deep...

The next day, we had a water feature:

The builders then came round and showed us how to dig a real trial pit:

A 1.5m deep puddle (over the course of 7 days the hole was half full of water)
Perfect for catching naughty cats!

So our ground conditions are a bit iffy.  No sign of any bedrock, just this orangey clay which goes on and on.  There's a high water content, but given our proximity to the river Itchen thats no big surprise.
Having considered piled foundations, we have been reassured that standard strip foundations will be sufficient, probably at about 1.2-1.4m deep.

Next post will contain diggers!!!