Cheers for the advice guys, will be buying some Castrol this week at 10W40, but just to be safe I'll keep an eye on the compsumption
Just for reference, Halfords is £32.99 for Power 1 Racing (4 Litres) IIRC, normal Power 1 is £28.99, so get it the Racing stuff for about about £29 with the discount card...