Why anyone would set off for an IMC lesson requiring DME for example without it working is pure madness, even worse is the person then paying for the lesson! Walk away and find a place that has spent the money on fitting or fixing the required equipment, yes its expensive but you are paying for it.
The school I used spent £5000+ on a couple of ADF's for the two PA28's I used/use. Its hard enough trying to learn new things without having to role play and make do with poor or U/S equipment.
Rant over.......