PIR Sensor - Replaces Wall Switch

I am replacing a light switch in a downstairs toilet that operates both the light and fan. The light switch only has two wires, live and neutral with an earth fixed to the mounting. Where do I attach the live wire - or is it the incorrect unit ?
If your existing light switch has only two wires in the back box it is highly likely that one is live and the other a switched live ie live coming to the switch and a wire coming away that becomes live when the switch is on. All movement sensors require a live and a neutral to work. You could look at using a ceiling sensor, this could use the live and neutral going to the light and operate both light and fan. The wall switch could then be removed. Do consult an electrical for more specific advice.

Do you have a model that works with only two wires so I can replace a pull cord switch.
There’s no PIR that can operate on just a live wire you need a neutral for them all to work - sorry

I currently have two wires common and a live out. There is a neutral cable in a connection block. Would this be used ok?
So long as this fitting can connect to a live and a neutral wire this will be okay. If in doubt we would suggest contacting an electrician.

Can this be used with LED lamps?
Unfortunately this is only for Incandescent/CFL/Fluorescent Lamps.

My current kitchen light switch wiring is 2 red wires wrapped together to be a top live in, 1 red wire at bottom as live out, and earth attached inside the box. Will I be able to use the pir switch and if so how would I wire it or would I need an electrician?
This PIR switch required a neutral wire, it sounds like your installation doesn`t have this. An electrician may be able to run a neutral wire from the first or last light in the circuit.

When you switch off the PIR will it turn the lights on by passing the sensor.
The switch gives you the options of 1) The PIR being on (per your set time) 2) The lights being on as normal so there is effectively no off option.

Does this have two live and two neutral connectors? This is the set up of the switch that its`s replacing
This has a live in, live out and a neutral. To wire this with 2 live and 2 neutral you just need to put the 2 neutral wires into the single neutral connector block.

Could I use this switch at the bottom of my stairs? I can turn hall light and upstairs light on at this point ...but only the upstairs light when upstairs ..ie 2 switches down but only one up
Your existing installation uses 2-way switches. You cannot use this product as the product only supports one way switching. Consult an electrician if you are unsure.

Can the sensor switch be used in a bathroom?
If you are planning on replacing your switch in your bathroom, we are certain that this would be in the right position, If you are planning on having it in a new position, you would need contact your electrician as there are guidelines where these can be installed in the bathroom.

Is this sensor a tree wire system?
Presuming you mean a `three` wire system, this requires a live and neutral wire, it requires no earth but has an earth termination block.

Im thinking of mounting this at the top of a stairs, will it pick up motion at the bottom? Its a 3 metre distance with a pitch of 47 degrees.
More than likely not as your requirements are quite specific. Equally the switching for your lighting will need to be 2-way switchable.