1998 Ford Festiva engine idle

Gday,

My name is nick & I live in aus.

Got a question with my WF Festiva in which I have a high engine idle (1200rpm) whilst the car has been running around doing stuff around the town? This high idle issue is only recent for about a month now but was normal before that.

Also, I have an issue for a while now with the idle before hand where, whenever I switch on my A/C whilst car is stationary my idle fluctuates up & down from nearly cutting out to about 1200rpm's constantly? I'm not sure whether is a part that controls the idle or whether it's my cars computer?

Would be awesome to get a rough answer to the problem & look forward to a reply.

Regards

Nick