You could use a step down tranni' as a supressed earth to give a decent
neutral potential to supply the house circuits, and reduce the fuel
consumption of the generator into the bargain, using the transformer
looped
from phase to primary winding, then on to the secondary winding and out to
earth. But as I say, both connections on an AC genny are phase, so it
literally doesn't have a neutral and is dangerous if used with
capacitative
loads.

You could ruin your tele' or damage any IF filters in other appliances if
they rely on a phase to neutral supply, so it then becomes a very
expensive
installation if you have replace everything. The grid itself is literally
phase and earth connections, but an AC generator is alternating phase /
phase supply.

I have a "power conditioner" rated at 40A - this contains a bloody great
transformer
(it must weigh about 50KG!)

It is not a step-down transformer, as the generator's output is the voltage
I require!

Excuse my ignorance, but how is a petrol generator different to the output
of the grid?
I was under the impression the grid's Neutral was connected to earth, so
they only need to run live cables - this being the reason people got
electrocuted - they touch the live, and this shorts to earth, or neutral!

We install isolation transformers in bathrooms, and on building sites, so
the neutral is no longer connected to earth, making electrocution impossible
unless you touch both live and neutral together - surely a generator is
safer then the grid, due to the neutral/earth isolation?

Please correct me if I am wrong, it is just how it seems to work from my
point of view!