l322 auto box fault

looked through lots of threads list seems seems endless
i have petrol 04 l322
my rangey been of road for few years until last few days, we took her out storage reversed no problem but went to drive forward moved in 1rst maybe 50yds then on change to 2nd can only describe like slipping revs went up to about 2500-3000 revs big clunk then trans fail safe message poor acceleration etc so looked on forum and topped fluid up with 1 bottle lucas trans slip everyone raved about and a further 1-1.5 litre turns out to be dexron 111 now seen another thread not to use it box was obviously low after topping took out again exact same but i tried using in manual mode box seems fine no problems goes up and down perfectly switched to drive everything fine till came to first junction 1rst - 2nd in drive clunk trans fail safe mode, stopped switched off tried manual mode all fine back into, drive fine no clunks no slipping till stop and try to drive from standstill trans fail on first change
any advice help on where to go from here? or drive for few days only did around 10 miles didn't want to make anything worse ??
cheers

Drain the fluid, change the filter, refill using the correct LT fluid using the correct procedure...(engine running, go through gears, box at 40degC, fill till you get a dribble out the filler hole - with engine still running) and see what happens....