It has the sports seats, so that is a good sign too.
Clea the stitching on the Steering wheel. A true M car has tri-colour stitching and the gearknob also has the M and stripes across it. It doesn't look like a homologation special as it has arm-rests.
It does appear to be a genuine 318is. Just a shame they never made tthat model anywhere near as good as the E30 for performance.