I last bought oil from a Ford dealer on Ebay at £6 per litre. Castrol 5w30 A5 spec as per mk2 manual. Sure it would be fine for the mk1, but check your manual. Came in a Ford and Castrol branded bottle. and way less than motor factors or Opie etc could sell the same stuff for. Bargain.
I use Blue Print filters via ebay CarPartsInMotion ebay store, and they are often <£5 if on offer.