Renault Trafic, diagnosis to this problem?

Hi,
My Trafic dci 100 1.9 [52 plate] has just developed its 2nd fault.
The first was it wouldn't restart when hot, having to wait a few minutes then no problem starting, or running.
This was when I was fueling up in Tesco's exclusively. Since stopping going to T's for my fuel this fault has cured itself?!?!
Right, now the current fault.
The glowlamp is now nearly always the last light to go out, used to be the first/second. Also the engine seems to be revving itself on idle and the water temp guage flickers up and down, with the cooling fan kicking in intermittently. Also there's an excess of dark smoke from the exhaust, and it seems more sluggish than normal going uphill. No problems with starting/re-starting, or with the engine cutting out, just these problems.
Can anyone help with this and offer some advice for a complete non-mechanic type?
Much appreciation in advance.

atb

CJ....