I need to install electrical bonding to my gas and water supply.

Unfortunately the gas meter, electric meter and rising main are
about as far apart as possible in my house. The water is under the
stairs in the middle of the house, gas in the garage at the front and
electricity at the very back of the house, which is a long thin
extended semi. I have a TT earth and can't see any point in
connecting the water and gas to the main earth, surely providing an
earth rod for each would do exactly the same job and it'd be a lot
easier. As I understand it, bonding the services (in a TT system)is
to ensure that if any part becomes live there is a low resistance
route to earth so the rcd trips, so an earth rod under the stairs
would do the same job as the main rod (earth is earth surely, if
there's a significant potential between two points 15M apart then the
worlds energy problems are solved).

I can't find any regs which say this is OK unfortunately, does anyone
know if I'd get away with it if I had to have an electrical
inspection. If not, is 10mm earth wire OK, are there limits on the
length you can use, and how it must be installed. Can I bury it? if
so, does it need to be in conduit (what sort?), how deep etc.

Any suggestions gratefully recieved, don't really fancy running the
earth around the outside of the house but even less keen on trying to
hide it inside. Could go up and through the loft but that'll be a
long bit of wire.