We have moved to a house with an extractor fan actually in the shower cubicle. I have read that this is ok as long as it is low voltage. How can I confirm for myself that the fan is a low voltage one or not? It is on the lighting circuit and has 1 brown, 1 thick brown and 1 blue cable connecting it.
Can you see what sort of cable it is - 'flat house-wiring cable' or 'flex'? Is there also an 'earth' wire visible in the cable - either a bare one or one with green/yellow insulation (even if it's not connected to anything)? The 'thick brown' one is probably one of a different colour which has had brown sleeving put over it - can you see what coulour it is underneath?
Since someone is bound to point this out (or tease you!) if I don't, as far as electricians' terminology is concerned, mains voltage (nominally 230V) is 'Low Voltage' (LV), where they call really low voltages (12V or 24V) 'Extra Low Voltage' (ELV). From what you've said so far, I suspect that your fan may be mains voltage.
Kind Regards, John