Bit of a head scratcher...
Is there anything directly above it/them in the trees?
...Anything that might be dropping blobs to create this object, a bit like drips forming a stagmite?
(I'd suggest a bat roost, but the object looks too well-defined in shape, and the blobs are/were too wet.)
If you put your ear to it (and/or to a straw with the other end poked underneath it), do you hear any buzzing?
I examined the football mounds again today, In fact there are 3 in all. One about 10-11 inch diameter, another about 7-8 inch diameter and a third much smaller. The main purpose was to try and identify whether they had entrance holes. Although the balls are covered in mud and I was expecting them to be quite heavy they are in fact very light, almost sponge like with no apparent entrance. Also when picked up they are squashy and emit puffs of brownish dust/spores. I therefore assume they're nothing to do with insect nests but some form of strange puff ball type fungus.
Ah - that's interesting.
Perhaps a relative of the woodland fungus Sparassis crispa
Fungi usually change their appearance as they go over, and I don't know what an old Sparassis would look like.
Need a mycologist...
The British Mycological Society has regional recording groups.
The Warwickshire one is here
As well as general info, that points to http://freespace.virgin.net/william.moodie/wfs.htm
I suggest you get in touch with them; perhaps they'd like you to show them the original specimens, but I'm sure an emailed photo would do in the first instance.
You might also see if you can get hold of:
A Fungus Flora of Warwickshire
M.C.Clark (Ed), 1980
ISBN. 0 903130 05 X
(I note there are '2,600 fungi and lichens found in the county')
Please let us know the outcome!
Thank you to everyone who has commented particularly basquesteve and Mike Hardman. As suggested I have contacted and sent images to - http://www.britmycolsoc.org.uk/mycology/recording-network/groups/warwickshire/