Vivaro - "check anti-pollution" warning and coolant loss

[Freki]

I have had this warning light on for months - garage has looked at it and found nothing obvious. They clear it and it comes back after a few days. We assumed it was EGR-related. So van was finally booked in. Van broke down on the M6. Van relayed to garage and they replaced (both? - i didn't know it had 2) EGR valves and also turbo was knackered. £2300 later, van drives out, working fine then 250 miles down the road, same error message comes back.

In addition - coolant loss is constant. No leaks visible. Pressure test passed. UV dye used - nothing seen. No coolant in oil. No steam in exhaust. Typically 1/2 litre of coolant needed every 100 miles to top up to expansion tank level - if i do a long drive and forget to top it up on way home, i get "engine Stop".. so i fill it up and away we go.

I have no garage who seems to know what is wrong and i cannot afford to keep spending money on it, on the off-chance they find something.

Looking online, others seem to have similar issues but no solution is ever published.

Any help at all from anyone on either issue - are they related?

Many thanks in advance