The nearest supermarket is indeed the goodings opposite DTD. It is v expensive and if you need more than nappies it may be worth considering a delivery from gardengrocer or we go shop.
we used wegoshop last year for basics, they delivered on time on arrival day, they were very good, polite helpful and explained any subs they had made. we had sun block, toileteries and water juice, snacks etc delivered to PORS. To the door of the room, i presumed (naively!) we would have to transport them from the recpetion area!
she was very kind, seeing how tired we were she just got on with it, put all the toileteries next to the sink and juice boxes in the fridge!!
it did cost about £15 (vague recollection, you d have to look for a more accurate price) but if saving taxi fares and time is what you re after, consider using we go shop.
ps you only pay what they pat, there is no mark up - again youd have to check again. we did it all buy email - we logged onto an american web based supermarket, shopped then cut and pasted into an email! worked well.
HTH
Tracy