td5 clutch, help please

I have had a new clutch fitted to my td5 defender at a local garage, it has been a disaster and now I am in a panic about what they are doing.
When I collected it the clutch was slipping in 4+5 and I couldn't go any faster than 50.They had fitted a clutch plate, pressure plate,thrust bearing and I had supplied a new slave cylinder.
I took it back and they "fixed it," the clutch now was right on the bottom and crunching into gears, I took it back and they said they had changed the push rod as the old one was shorter I don't remember a push rod with the new cylinder. I think they cut the old one down. I took it back again and they said take it back next week.
Could some one tell me the correct procedure for installing a new clutch and how it should be adjusted before I go back to see them

you should never need to alter push rod if parts are correct and fitted ok,there is no adjustment to the clutch you should really change dual mass flywheel at the same time ,did they check plastic bush in release arm ,shortening rod would maker pedal worse lengthening it would bring pedal higher and eventually would make clutch slip as would be pressing on clutch,perhaps only needed bleeding but why was clutch slipping ?

I had a new gearbox fitted and there wasnt any thing wrong with clutch, but they suggested it would be better changed while the box was out, they put new clutch in and it was slipping straight away . The landy has done 55k from new and there was no problem with the old clutch

as my post above yours ,it is possible to get a poor clutch kit ,ive had it happen a couple of times ,if clutch plates fitted wrong way round it usually jams so you cant release drive,something sounds fishy 55k isnt long even for an r380 ,change oil regulary with your new one if it is new and not an old box ,at least yearly

Thanks for that, I will see what they have to say before I take it back, box was rebuilt as I had damaged casing, nothing wrong with new box