auto lock up problem

hi all , firstly thanks to all who have posted to previous threads on this subject,
my clutch lock up works when its cold for a few times , then as it becomes hot it sort of comes in half way , it is in enough to keep engine revs up on the overrun but any amount of throttle it will drive like its not locked, but then it will randomly lock and not slip ????
so i think it has a sticking valve in the transmission?? so before i get involved in stripping the valve body and inspecting it i would appreciate any input from the forum members, anything i missed ??etc
regards and thanks , mel ,

try this http://www.amazon.co.uk/Lucas-Transmission-Fix-Shifting-fl-oz/dp/B000ARTZPO

That looks good , does it work tho , must admit I'm a bit sceptical if additives , if the consensus is a valve I will strip it and clean out , from what I read it doesn't seem too difficult .. Thanks anyway , mel

i didnt use it myself as i have a manual but a friend of mine did based on the good reviews from the web... worked a treat ... IMO for 15quid worth a try before you strip the box, that's what i would do if i was you cos even if it doesnt help in your case it wont huirt that's for sure... dont be sceptical with additives they were conceived by engineers