>Your last suggestion sent it into a hissy fit - I think I'll have to call it a day my brain hurts - when you say use an anonymous type how could that help ?

You could do something like this (based on the simple invoices example I posted earlier):

            var query2 = invoices.GroupBy(x => x.clientid)
           .Select(group => new { Id = group.Key, invs = group.OrderByDescending(x => x.invoiceamount) })
           .OrderByDescending(group => group.invs.Sum(x => x.invoiceamount));

            foreach (var q in query2.ToList())
            {
                Console.WriteLine("\nClient Id: {0}.", q.Id);
                foreach (var x in q.invs)
                {
                    Console.WriteLine("\t{0:C}", x.invoiceamount);
                }
                Console.WriteLine("\n\tTotal: {0:c}\n", q.invs.Sum(x => x.invoiceamount));
}

The last .OrderByDescending is just a frill so that the clients are listed in order of total invoices value.