Obviously price will depend on your area and what they charge.

Announced on their Twitter feed

Sainsbury’s PR ?@SainsburysPR
Good news! From tomorrow (12 June) we’ll be cutting #petrol & #diesel prices at our petrol stations by up to 3p per litre

Sainsburys knocking upto 3p a litre off fuel (Petrol/Diesel) from tomorrow (12/06/12)