An update on my partner's application. My EEA partner (Greek) received his PR card today in the post.
The timeline:
Application sent: 4th April 2015
Application received: 8th April 2015
Acknowledgement of receipt: dated: 10th April 2015
Payment taken: 13th April 2015
PR card: received today 19th May 2015 (Dated 15th May 2015)
On the whole processing time was about 6 weeks (though taking into consideration it was the Easter break and a Bank Holiday between processing-so in all a good time span!

Thanks for this great forum for all the advice-I'm sure I'll be needing more in the months to come!