Dexs.
Hello,
Is the KMS Compressor AS186 any good? If not could you recommend one to me please.
Many thanks
Dexs.
Dexs, welcome to the forum.
The "KMS Compressor AS186" is typical of many made-in-China, single piston with tank airbrush compressor. It can work quite well for modeling. I reviewed a similar unit awhile back. It costed me $40 plus shipping from Northern Tools in the US last year.
The problem with these Chinese compressors is their quality control. If lucky, you may get one that serve you well for many years. If not, you may need a new one in a few months.
You should test your new compressor by running it continuously for about 30 minutes or so. Push down the airbrush trigger to force the compressor motor to run constantly. The compressor head temperature should stablize and stay at no more than 20-25 degrees C above room temperature. The compressor head should not be hot to the touch if you cannot borrow a laser thermometer from the kitchen. 
If the compressor is working normally, this test will not hurt it. If not, it is better to know that you may have received a low quality unit when it is still under warranty. In reality, the compressor should run much cooler because the motor is on and off intermittently in normal modeling.
I prefer a twin piston over a single piston with tank. The twin piston runs cooler and quieter, thus, probably last longer. Even with a tank, the compressor motor still kicks on and off according to the airtank pressure, but less frequent. Because it does not synchronize with my trigger action, it is may be more distracting. I can live with either.
If your budget allows, you can get a Revell comparessor for a little more. It is much more dependable. The Revell Master Class Compressor is an oil-free double cylinder piston compressor with tank. It should run much cooler and last much longer.
Good luck. Let us know what you decide and how it works out for you.