Yes, you can use the 9-pin from that 13-pin header to power bluetooth.  Just leave the other 4-pin open (toward the coin cell battery direction).

@Chino de Oro​ Thanks for the confirmation. I'm very grateful

Glad to help out.  If my answer resolve the query, you can close this thread by marking helpful post as accepted answer.

@Chino de Oro​ I also contacted the supplier of the PCI-E Wifi adaptor with details of my computer but they said it will not work with the 5040.

Alignment of pins and orientation of plug compatibity OK but I've played safe and returned it so now need to find another fully compatible unit or go down the through the power cables route and cat 5/6 direct to router. Cheers anyway. 

Afraid that the supplier has provided misinformation.  You should of test it out and return it if it did not work.  Most if not all brands use the same standard 4-pin cable to connect to 9-pin internal USB to power bluetooth.  I have used a 5040 SFF before for testing several wireless with bluetooth and low profile graphics cards.  The 9-pin worked well with different brands as internal USB.