I picked one of these up just recently and it looks like it would be a decent platform for a suppressor. so does anyone know how to remove the barrel so I can get it threaded? it's very much like a walther TPH.

It's pressed in.
You have to make a simple barrel press, similar to those used to change barrels on the Walther PP series, and the Markarov.

Gun Parts sells parts, and have a fair exploded view:
www.e-gunparts.com/productschem.asp?chrMasterModel=0770zTP22

The press is basically two pieces of flat bar stock joined by two threaded rods.
One piece has a plastic or brass pad to protect the muzzle, the other fits the frame just behind the barrel and has a hole that will pass the barrel.

The front part fits over the muzzle with the pad touching the barrel, the other end is over the frame end with the hole centered over the chamber end of the barrel.

After driving out the barrel retention pin, the nuts on the top part are tightened, and the barrel is pressed out the rear.

To replace the barrel, the tool is turned around so the hole is on the front of the frame and the barrel will pass through it.
The rear section is put over the barrel with the pad on the chamber end, and as the nuts are tightened, the barrel is pressed IN the frame.

thanks a lot, I looked but I can't see a barrel retaining pin or a hole for one anywhere

The IJ may just be pressed in extra tight.
This could be a problem since the frame might distort if you use the above referenced home-made press tool to remove it.

Another option is to use a tap die with a guide stud that fits down the bore to keep the die straight.

This is how AK-47 owner's thread the muzzle of un-threaded barrels.
The die set has a steel pin that's a close fit in the bore, and this serves to keep the die aligned straight on the barrel.

In this case, it'd have to be a custom set.