Freeserve and group Emails

Anyone experiencing problems sending group Emails through Freeserve? I regularly send Email to 2 "group" recipients, both made up from address's in my WAB. One group has 16 address's and the other has 31. Over the last 3 months mail sent to these groups is taking longer to get there, last week it took one Email 3 days to reach the recipients. I am currently awaiting an Email that was sent to both groups yesterday. I have tried deleting the old groups and making new ones (same people of course) but still the problem persists. Emails sent individually are almost instant and I am not experiencing any other problems. I have contacted Freeserve helpline who were far from helpful and are unable to come up with anything.
I am using XP pro, Outlook Express 6 with a Freeserve Broadband connection.
Anyone got any idea's ?
Regards
FBW