Anyone know how to get ZE from Scottish Power ???

Tony, your site is pulling about 400kVA from your figure. I presume you have a local Transformer, which is close to you. The supply type doesn't matter the Ze will be very low whether TN-S or TNC-S, although most likely TN-S. It will certainly be low enough to open your main breaker of whatever type (Fuses, ACB, etc) for an Earth fault at the main switchboard. It will be much less than the 0.35 Ohm figure above, this is for supplies to 100A that are TNC-S. What size are your incoming cables, this will give you something to estimate its likely value from the length and size, remembering that the N-E bond will probably be at the TX? If it is a private supply the bond may be at your switchboard which will give Ze of essentially zero. You can check this by the metering position, the primary or secondary of the TX, if primary it only supplies you.

Tony, your site is pulling about 400kVA from your figure. I presume you have a local Transformer, which is close to you. The supply type doesn't matter the Ze will be very low whether TN-S or TNC-S, although most likely TN-S. It will certainly be low enough to open your main breaker of whatever type (Fuses, ACB, etc) for an Earth fault at the main switchboard. It will be much less than the 0.35 Ohm figure above, this is for supplies to 100A that are TNC-S. What size are your incoming cables, this will give you something to estimate its likely value from the length and size, remembering that the N-E bond will probably be at the TX? If it is a private supply the bond may be at your switchboard which will give Ze of essentially zero. You can check this by the metering position, the primary or secondary of the TX, if primary it only supplies you.