Basic/should be there - loo roll, kitchen roll, tea, coffee, milk jiggers, salt & pepper, oil, washing up liquid, dishwasher tablets (enough for every day booked), dish cloths, scourer, tea towels (more than 1), soap at whbs, washing powder if there's a w/machine, bin liners.
Nice extra - fresh milk, Cafetiere & coffee, basic herbs/spices, extra towels, shower gel/shampoo/conditioner, foil, clingflim, food bags etc.
Nice touches - wine, local butter, bread, cheese, fruit etc. beach towels, well stocked kitchen cupboards.