Renault 11 GTL runs fine until I slow for a junction and then it wants to stall.Any ideas.

Could be a few problems:

The main one l have in my mind is a problem with the charging system

Charging system - the alternator provides more charge to the battery when engine turns over quicker, this is why if ur engine is idling & u turn on the headlights or air con, the car starts revving a bit higher. When u slow down at a junction less charge is being given to the battery so it is liable to stall.

Could be the battery is on it is way out.

There r other things l can think of, but u would tend to get those problems at low revs anyway e.g. when u start the car, or engine is just idling for instance a faulty idle control valve/sensor.

My advice is take ur car to a garage. With a multimeter they can easily check the condition of battery & whether the alternator is charging properly, they r quick & easy checks & they should really do them for free.