Yesterday after work I went to start my 1997 Felicia 1.6 and it had real trouble starting. It would start to catch and then the revs would drop off and it would die. There was no problem cranking it as the battery is fully charged. Eventually it decided to start and I got home with no problems. I did notice however that the idle speed has now decided to be about 600-650rpm instead of the 800-850rpm it was before. This morning it started with no problems at all - instantly - and I got to work with no problems. The idle is still at 600-650.

Any ideas on what has caused this?

It might be worth cleaning the throttle body out - this often causes problems especially if muck gets around the opening. Alternatively the temperature sensor can effect the running of the engine, if cleaning the throttle body doesn't help then a new temperature sensor might be the next best item to change. I hope this helps a bit - Im sure other people will comment shortly!