This does happen sometimes. The tip is sent in the internet language HTML and some older e-mail reading software doesn't support it properly. The best thing to do is upgrade your e-mail reading software to the latest version.
Alternatively, the weekly email is always duplicated in a fully readable version on the site. To see it go to www.moneysavingexpert.com/latesttip. You could consider the 'not so readable email' as a reminder to come to the site and read it properly there.