Hi Sam.
Thats no problem; "client side" is just agency lingo; "agency side" is working within an advertising/design/creative agency designing and creating campaigns for their clients/customers, "client side" just means working as a similar/related role in the customer organisation, i.e. G/F works for an agency called TBWA in Didsbury (i.e. agency side) they do work for GHD (the straighteners), but she liaises with the marketing team within GHD to design the promotion (client side). I hope you understand that??
Same kind of principle applies for printers to an extent, you can work internally in a printers or you could work as a print buyer, for example, for a customer (client side); you get me?
Any way, what I would advise for you is to see if there are any print production assistant roles in an agency, they crop up quite often. dont just keep your eggs in one basket in terms of recruitment agents, I had my CV in at 15 - 20 of them all over the place! try; Blue Skies, Orchard suits, Aquent see what comes up there.