Hi there.

I think I need a ride height sensor Disco 2. Anyone know where I can get one and how much?

Thanks

Part number: RQH100030. Available from almost all of the usual suspects, Paddocks, Craddocks, and any number of suppliers on those auction websites. Costs anything between 20 and 60 quid each depending on where you buy them and the quality you choose. On average, about 25 quid is what most people pay.
Remember to disconnect the battery before you do anything to the ride height sensors or else you could end up with suspension calibration issues.