Ok, here we go, a quality resort, no children if possible, quiet, in nice grounds. But a short walk to a buzzy marina or town for evening meals and people watching. Hope its not too much to ask!! We have done all the Benidorm type places and are getting on a bit older now if you know what I mean. Oh and a flat walk to a beach!!
Try looking at Torremolinos, not the same these days as it was in the 60s and 70s mostly Spanish visitors these days. Been looking at it myself instead of Mallorca and there are some nice hotels along the beach and unless you want to go into town it is all on the flat with a Marina close by. The link below is for a hotel where you wont get many children.
Its easily accessible from Genoa Airport (which is served by BA from Gatwick, Ryanair from Stansted, Thomas Cook from Glasgow, Manchester & Gatwick and Thomson from Birmingham, Manchester and Gatwick). There's a train service from Genoa station which hugs the coastline all the way.