Yahoo Uk is rather an old style webmail client and their servers are the same as 2002 using Windows Server 2003 which is hackable. Yahoo Germany was moved to bsd/linux based servers and their webmail clients are more stable. I would advise anyone not to use yahoo/hotmail for personal stuff( banking, sensitive data ).
There so many scripts/hacks online which allows to hack these emails. A yahoo email client is easily hacked within 2 minutes. I personally use a private webmail. You can get these really cheap on the net.
Hotmail is under a serious flaw at the moment. Due to a high demand of new domains , most of the providers are trying to cope with new style ( ipv4 to ipv6 ) .
Be safe online !