How can I fix my Peugeot 307 HDI, Anti Pollution Fault?

I have a few problems with my Peugeot 307, I needed some advice so I don’t get ripped off.

It’s a 307 HDI 2.0 D Turbo 110 BHP, 53 Reg, about 52,000.

The Engine management light is on and often while driving the dial flash STOP ‘Engine Coolant Temp Too High’. Also it will say quite often ‘Anti Pollution Fault’.
The car doesn’t drive the same, infact it’s quite sluggish.

I have took it too Peugeot whom wanted a ridiculous amount to fix.

This is what the report says.

Engine ECU

EDC15C2
Permanent fault, EGR solenoid valve, EGR solenoid valve circuit short-circuited to earth or open circuit.

Permanent fault, Particle filter, PEF pierced or differential pressure info incorrect.
Intermittent fault, Engine coolant temperature signal, Short circuit to positive or open circuit.
Intermittent fault, Additive quantity, Additive ECU.
Intermittent fault. Additive quantity. Maximum additive in PEF threshold reached.

They also said if you sort the top two (as above) then all faults will go.

What’s the best and cheapest solution?

I will also try with more expensive fuel, I do sometimes get supermarket fuel and try turning fuel cap a few times.