B7 100 HST pto grinding.

First of all , greetings from downunder .
After searching this forum I still can't quite find the answer to my Kubota's problem.
I bought my Kubota B7 100 HST 4X4 secondhand.
Since I have had it , it has always had a very slight grinding when putting the pto in for the mid mount mower.
Recently I hit a small stump and the tractor stopped , I started it again but now I can't engage the pto for the mid mount mower , there is a severe grinding and it won't engage .
I have tried dropping the revs right down as suggested on this site , but still the same.
I can engage the rear pto with no grinding , but there is nothing connected to it.
I have greased the nipple for the throwout bearing.
If I engage the pto before starting the engine all is good , but I'm guessing this is not advisable.
Another thing , when the pto is engaged and engine running , if I push the clutch pedal in , the pto stays engaged , should it disengage ?
Your help would be appreciated,
Cheers,
Greg

Well it looks like the clutch disk is frozen.
The tractor still moves with the clutch pedal in.
I tried a couple of methods mentioned on this site to free it up.
Tied it to a big gum tree as well.
No go.
Looks like i will have to split it when winter gets here.

Well I split the tractor and the clutch disk was shattered and a spring was stuck behind the flywheel.
The disk was also stuck on the spline.
Does anyone know of a cross reference for a aftermarket disk or if some other vehicle uses the same disk ?
The Kubota brand one is very expensive down here in Australia .

The pressure plate looks like it is alright.
I did see the discs on ebay , but with the low Aussie dollar and postage it still works out to about $100 lower than the price I was quoted ($235)
As my paddock is getting out of control I need to get the Kubota going real soon .
Just thought there might be a cross reference .
They also want $140 for 20 litres of Kubota UDT