Depolution Fault - EGR Valve - Peugeot 407 2.0 Hdi (136bhp)?

I have a Depolution System Fault warning on my centre console which comes on when I start then goes off and I have an Orange Engine symbol which stays on, on my centre dash & a smaller one to my right.

Diagnostics from maindealer show

1. Permanent Fault. Additive System. Fuel Cap present sensor fault.

2. Permanent Fault. EGR Valve circuit. Valve position too distant in relation to the reference valve.

3. Permanentt Fault. EGR Solenoid Valve. Test of clearing on switching off the ignition not correct.

Have move away from main dealer to specialised dealer as due to cost. Specialised dealer has fitted No 1 above, (Fuel Cap Sensor) on my instructions (No Diagnostics),

This has cleared No 1 & 2 faults above, I was hoping for all 3. No 3 still remains so Depolution warning still on.

They have suggested in this order:

A. Add Addittive Fluid, £11.00, run for 2 wks, make long runs, run diesel low, see if it works, which I have done 9 days in now, no luck so far.

B. Do Dignostics, £42.50 + VAT, if required do Download for upgrade software extra £30.00 + VAT

C. Fit EGR Valve, all in £ 326.03 inc VAT.

HELP PLEASE, any ideas in what next steps should be, any other ideas / solutions, clean, reconditioned EGR Valve, etc.

Car is starting to cost me a fortune, only had car for 3 weeks, car has only ever had 1 driver from new + me & milage is only 42,000 genuine miles on an 04 plate.

Any advise would be much appreaciated !!!