i've seen it written out like htse, but i just can't seem to make that noise!
I'm not surprised you can't make that noise. Try this:
Start by making a gutteral 'h' sound at the back of your throat - like you want to clear your throat when you have a, shall we say, very wet cold.
Now, keep that going, and then finish it off by saying 'tse' like a chinese person who is slightly cross.
That's roughly it. Practise that lots of times (it should sound quite extreme), and then when you can do that, try relaxing and softening it all a bit. Make it the same basic shape, but gentler. And hey presto.
Then try it on someone Polish. : )