I use Orange web mail. After a few days my mail builds up to perhaps a total of about 50 after which I seem to lose most of the items. There are still one or two of the earlier items in my In-box and then mail flows in until the same thing occurs, and I am left with the said earlier items. Where do the items vanish to and is it possible to retrieve them or are they lost forever?

You need to ask Orange mail this. Most web based mail services have a limit on the size of your mailboxes and the length of time mail is kept. But if they purge the mailbox, the mail is gone.