Help please T4 smoking and spluttery

I’m new and this is my first post, my lovely T4 is blowing out white smoke on start up and whilst driving, took it to the garage as it was spluttery and sluggish when driving they fixed a lot oil leak, fuel leak and change the timing belt as the timing was wrong and was fine when we picked it up, but then a few days later started blowing smoke out again and engine seems spluttery. Has had full oil filter change injectors took out and tested and cleaned they cane back fine. Taking it back tomorrow any ideas I can put to him to check for? I have read about the glow plugs being changed as this can lead to it being smoking but also I had to hit starter motor this morning to get it to start