X-rated (Halfords) Mountain Bike for Repair (Charlton SE7)

It has 26" wheels, inner tubes and tyres, a front disc brake, grip gear shifters, mud guards, pannier rack etc. It needs a new rear derailleur which snapped off so it is not rideable until it is repaired. It has not been used for a few years and even though it was under a roof it did get a bit rusty from exposure to air moisture. It could do with a new chain as well.