Tim S wrote:

Sounds more like TN-S to me (that's earth (Terra) Neutral Separated IIRC.

Agreed.

Technically, only an enquiry to the supplier will be reliable

Huh... Under the ESQCR it should be, but the reality seems to be that
DNO's records of older installations are often incomplete or just wrong
and they'll be unable to answer the question without making a visit,
which may be chargeable. Ditto if you want to know what size main fuse
is fitted. This is a frequently discussed topic on the IET wiring regs
forum.

[Tariff change]
Sorry - don't know. Phone call to the network operator or meter operator
technical dept, or phone Ebico and see if they know what will happen?

Customer contacts supplier and requests tariff change. Supplier
arranges for their meter operating company to change the metering
equipment. DNO is not involved. Customer should keep their own records
of old and new meter readings, just in case of a billing screw-up (not
unknown, check bills carefully). In the case of a change from E7 to
general domestic tariff the meter will be changed to single-rate and any
time-switch equipment will be removed (IMLE, YMMV).

--
Andy