There are a number of books called "Moreton Wirral A Pictorial History
" written by Frank Biddle (local farmer) and Alan Fellowes which have loads of photos of the caravans.We have 4 volumes of the book. They are on Sale
at Amazon http://www.amazon.co.uk/Moreton-Wirral-Vol-Pictorial-History/dp/0907768598.
I will have a look later to see which volume has best pics of the caravans and let you know. You often see them in local charity shops and I think the ice cream shop at Parkgate may have similar.
Birkenhead Market is also a good source of old pics.