Browsing in my local (Ayr) branch and spotted this at £8.98/litre, marginally cheaper than Opie oils and possibly more convenient.
Castrol Edge Motor Oil 5w-30 Fully Synthetic 1ltr | Motor Oils | | Car Care from Wilkinson Plus
Castrol Edge Motor Oil 5w-30 Fully Synthetic 1ltr | Motor Oils | | Car Care from Wilkinson Plus