I have yet to receive a response from my server administrator, but I appear to have resolved this, at least temporarily, but still do not know how this came about. My lists were initially exported from MBM which was set at UTF-8 universal encoding. I therefore assumed that the exported files were correctly encoded. I have just managed to correct the problem by downloading the files, saving them as UTF-8 and then overwriting the files on the server. Let's hope they stay that way.