Simon Hawthorne wrote:

I've been out and dug a hole (inside the barn) to try and establish
how deep the footings run. I have put a photo and description on my
web site (at the bottom) - I reckon they are 2' in total - I reckon
this isn't enough?

It's more than our 70 year old house has. You need to assess whether
there's been any movement recently. If not, and if you're not intending
to add to the load (by extending upwards for instance) then you won't
need to touch the footings.

--
Grunff