As I understand, the UK grid does not have the capacity to 'store' excess power imports. The government pays wind turbine operators around GBP 3 million a year to shut them down when the grid is at capacity.
If shifting general freight for nationwide distribution by rail was realistic other countries would have adopted it. Point to point delivery by road will continue to be the cheapest and practical option.
Presumably Cambodia imports these from Thailand because it needs them for its transportation and energy sector. How long before their reserves are depleted and their economy is adversly affected?