Hard Start

Hi Guys.
I'm having trouble starting my disco TD5 in a morning and when it's been sat at work all day.
Once it does start it runs mint. There is a puff of white smoke once it fires up but then no smoke at all when running.

Would you say my 1st job would be heater plugs?

Thanks in advance.

Testing the heater plugs are functional could be a good starting point.

Thank Discool. I'll replace them 1st. I had planned on replacing them at some point anyway as part of my service.
Thanks again