One option might be to use a voltage regulator, these consist of a multi tapped transformer with the correct tapping automaticly connected via quick acting circuitry.
Such devices can correct for both low and high input voltages.
The UK spec ones will give a 230 volt output (plus or minus 6%) from an input that varies from 190 volts to 270 volts.
Start with about 270 volts, easily obtained from 240 with a buck.boost transformer.
Off load 270 will be fine at the far end since it is within the range acceptable to the regulator.
The on load voltage can drop as low as 190, and still give an acceptable voltage output.
A second transformer could step this down to 120.
For limited use, this should work fine.
For a long-hour load though remember that the energy wasted in the cable costs money, a larger cable might pay for itself in a few years.
Other options include not useing utility power at all, but purchasing a generator, which if portable could be used elswhere.
If relatively large loads such as power tools with large starting currents are to be used, but only occaisionly, then it might be worth the use of a large inverter and a battery bank.
Charge the battery from the 240 volt supply useing a switched mode charger with a wide input range, or use PV modules.
Going down the PV and battery route has the merit of not paying forever for the iron losses in at least 2 transformers.
Off load losses could be 120 watts, or say 1,000 KWH a year. Depending on power prices, that might cost $250 a year, forever before any energy is usefully consumed. Add to that perhaps 25% losses on load due to copper losses in the transformers and cable.
Considering that PV also saves the cost of trenching, it might be economic.
