Iv just purchased a 2000 focus on now the temp gauge goes to the middle perfect but no heat comes out the vents you have to rev the car or be driving be for it starts to blow hot hair but I'd you stop it goes back cold ?

Check the obvious first like the coolant level. Also the thermostat housing itself can leak on the MK1.

Would that affect the heating being cold and the temp gauge not moving from half way ? Surly that would make the temp rise

Sounds like the heater matrix needs checking.

A broken matrix will stop it heating up properly except when the fan is at full belt.

Also do you know when the pollen filter was last chsnged?

A dirty or wet filter will reduce air flowing through the heater and hinder efficiency.

Is the matrix hard to get to ? And we're is the pollen filter located ? All so I'm not 100% weather mine is a mk1 or mk2 it's a X plate

It's a MK1.

The filter is under the scuttle at the base of the windscreen, there is a removable panel to one side.

It is recommended to change the filter and seal at the same time.

The heater unit is behind the glove box, you need to remove the footwell trim, glove box and you have access to the heater motor and resistor.

It's usually the resistor that is at fault and is to the right of the motor (usually behind some soundproofing foam).

Cool il have a look I thought the resister only controlled the speed of the fan not the heat

Do you need a pollen filter ?

Do you need a pollen filter ?