Right, well I might as well update this with the progress made.
This was 2pm on Sunday;

Yep, an archeological dig
And to give a better idea how much concrete and soil had been shifted by hand, this was where all that ended up (that's a 4c.yd skip);
An hour and a half later, all the mesh was cut and fitted. I was too busy cracking on to take any pics then. Here's a pic half way through filling in the hole that just kept on taking...

That's a layer of A393 mesh in the bottom, on 50mm chairs and another layer on the top (they'd not been able to deliver the correct spacers so I had to improvise with blocks of precast!)
We started mixing and pouring at 4pm, my mate left at 10pm and after 133 bags of C40 concrete, at 1:15am, it was full!
This is what it looked like last night after 18 hours cure;

(expertly troweled off with the back of a shovel!

)
A bit of a scrape and clean around the edges later;
So 2 weekends work and the floor is back where it started

(but a jobby load stronger!!!)
I ran out of time and concrete to do the rear pads, so they need to be done this weekend. About 4 hours work placing the re-bar and then mixing by hand in a wheelbarrow I think...