Where can I obtain train tickets for travel to/from Poland and the Ukraine?

I am based in the UK and need to book a 2 berth sleeping compartment for return travel from Katowice to Kiev.
I am advised to book this route as availability can be tricky.
I have tried DB, all the usual European booking agencies and all suggested on seat61.com but unless I am based in Poland or the Ukraine, it seems to be very difficult.
All advice appreciated.
Thanks for the advice.
I was already aware of Real Russia as I have used them before for Visa's.
I found several companies offering tickets but sadly, they all want to triple & quadruple the ticket price with commission so I've decided that when I do go, I shall build in an extra day or two (in the event of availability issues) and will buy at the station.

You could try going through a travel agent. there will be a fee on top of the train fare, but it'll prevent pissing about.

Or try http://www.realrussia.co.uk/main_train_screen.asp
they're a UK based firm, you can book from there. Kiev is under KYIW

Edit: Fisrt link didn't work...does now though.