As a rough guide, multiply the numbers shown there by 0.122 (because electricity costs about 12.2p per kWh on many tariffs) in order to get a cost in pounds and pence. e.g. for the Aga City60 it's stated: "To cook a standard weekly menu: 32kW". Multiplying that by 0.12 gives a cost of £3.90 per week to cook the menu shown towards the bottom of that page.
(To 20p per unit cost of electricity used on that page appears to include the standing charge element, which I excluded from my example above, meaning that you need to reduce the figures shown on that page a bit to get a fairer comparison).