Can I use a normal extension lead with a charger?

No. Household extension leads overheat under hours of high current. Use a heavy-duty, earthed cable with the same plug type and an adequate cross-section.

Can I plug a three-phase charger into a household socket?

With a suitable adapter, yes – but the charger then works on a single phase at up to 16 A (about 3.7 kW).

Adapters & Extension Cables

Bemis EV Charger Plug Adapter – Household / CEE Plug and Socket Adapter$10.90

Bemis Heavy-Duty Extension Cable for Portable EV Chargers (5 m, 10 m)$21.90

Choosing the right adapter and extension cable

Portable EV chargers draw high current for hours. If the socket doesn't match your charger's plug, you need a plug adapter; if the socket is far from the car, a heavy-duty extension cable rated for the charging current. Household extension leads and power strips are not suitable.

1/16A: standard household socket (Schuko), single-phase 16 A.
3/16A and 3/32A: blue single-phase industrial (CEE) socket.
5/16A and 5/32A: red three-phase industrial (CEE) socket.

An adapter can't exceed the lowest rating in the chain: from a household socket the power is at most 3.7 kW on a single phase, so set your charger's current accordingly.