diesel 1.9 hard to start when warm?

I have a 1.9 skoda felicia estate it starts first time every time from cold but when it`s warmed up it takes a lot of turning over to start it, just serviced including fuel filter,also put some forte injector cleaner through it aswell, been told it could be the temperature sensor so fitted a new one, but it`s just the same, also has a very slight miss when labouring in fifth or fourth gear, don`t know if the two are connected, any ideas anyone, thanks in advance if you can help.