If you have a local branch of Costco near you - try there. If you are not already a member you will need to factor in the joining fee, but some of the deals they do are very good - on oil as well. You have to keep checking with them because their offers change but oif you time it right they can be very cheap for good brands
Surprisingly for a cash and carry type operation that sells everything, my local Costco (Watford) has a good tyre fitting bay as well.
Ian