Clutch now stuck/locked?!

Hi, I posted a thread on here just over a week ago re: a problem with the clutch on my 1988 90 which I thought was now sorted, I was having trouble getting gears (mostly rev, 1st and 2nd) with grating etc and when pumping the clutch could just about manage it but I checked my clutch fluid and it was very, very low (hadn't checked clutch fluid in a very long time stupidly so don't know how slow it'd gone down) so I topped it right up (didn't bleed the system mind) and the problem seemed better initially then totally went away and all seemed perfect for a few days so never did bleed it. Yesterday driving along and went to drop down into 2nd and the clutch pedal just locked/seized cant't get any gears at all now. You can press clutch pedal down about an inch then it just hits solid and no way will it go any further it just returns up the inch on the spring! I'm guessing I never sorted what was causing the inital problem by just topping up and leaving? Clutch fluid gone down a little only (about 10-15 mm) from when I filled right up about a week ago. Is it likely to be slave or master cylinder or perhapes something inside housing like release bearing or selector fork. Or perhapes could it be I still need to just bleed the system and an air lock has worked through and locked it all up, or is this wishfull thinking?
Any help/ideas would be fantastic and I look forward any replies. Thanks Mark.

probably pivot worn thru lever you can check by removing slave cylinder

Thanks for that, I'll get out and get the slave cylinder off and have a look then. Just needed a pointer on where to start, I pressume you don't think it's the master cylinder then. Does the fact that the fluid level dropped 15mm in a week mean anything of any use? Thanks again Mark.

if master cylinder is leaking you will get a wet pedal ,slave cylinders often leak and more so if piston goes further out

I have just orderd a new slave cylinder and clutch folk with all relavant clips etc. Is there a chance it could just be the slave cylinder and I won't need to do the folk (ie get into bellhousing) I thought with the clutch now stuck solid and no movement though on pedal it must be the folk although slave certainly knackerd anyway and needs replacing. Is there any way I'll be able to tell if fork ok or not when I get slave off shortly.Thanks again.