"first urban settlement to promote seaside leisure"
A highly dubious claim.
Leaving aside what the Romans did for us .... (Baiae?) the mere title of "Promenade de Anglais" shows that it was built in response to the demands of rich English visitors. This commenced in 2nd half of 18C - but those people were merely replicating a fashion which had already commenced in England.
Scarborough is usually regarded as the "first" seaside resort, growing, in its case, out of its earlier "Spa" beginnings as the value of taking "sea waters" became a fashionable development of taking spa waters. Wiki notes that bathing machines were operational there from c 1736.
Scarborough has a lot going for it by the way - not as a potential WHS but for a pleasant visit to see its castle, bay/fishing harbour and its 18th/19th C buildings - the Grand Hotel which was one of the World's largest when constructed in 1865 and, for those interested in Geology and the history of Museums, its Rotunda Museum dating to 1829. http://en.wikipedia.org/wiki/Rotunda_Museum
Of course UK did consider trying to develop Blackpool as a nomination, being the world's first "popular" seaside resort, but decided against. Here are the conclusions of the review panel " The Panel agreed that tourism is a part of the development of industrialised societies which should be represented on the World Heritage List. Blackpool is undoubtedly one of the first places marking the rise of the popular seaside holiday, but the surviving major buildings are a half century later. Structures such as the main railway station, which were key to the whole concept of mass leisure, had been demolished. More information was needed on comparators to the surviving buildings and on nominations such as spas, also dealing with the rise of tourism. The Panel were not convinced by the case for a cultural landscape, which would have placed less reliance on the monumental buildings of Blackpool. They considered that the historic relationship with the sea, its main claim to OUV as a cultural landscape, had been changed by the new sea defences "
Given that the evaluation is probably correct in its assertion that tourism should be represented on the List one wonders if the Promenade de Anglais is the best example - though the domain probably justifies several sites covering different
b. Population - rich/poor
c. Types - seaside, adventure park, hotel, winter sports.....