I have had some very useful help from Jacob on an older version of Excel
where he sorted my problem out with SUMPRODUCT (see Problem with Syntax?
posted below):

=SUMPRODUCT(--(TEXT(B2:B20000,"mmyyyy")="012008"),--(C2:C20000="Motor"),(D2:D20000+E2:E20000))

The above formula works great, but I have two questions for Excel 2007 users:
1. If I convert B2:B20000 to B:B, why do I get a #VALUE error
2. Will SUMIFS do the above and if so, how?

Thanks