Citroen C5 2.2 HDi

I have owned the 2.2HDI SX Estate for about a year having owned virtually every Citroen to date from 2CV on. My last two vehicles were both Xsara Estates (not Picasso) and I traded up to the bigger C5 in order to tow a caravn and hump more gear to and from France. I went for the 2.2 HDI engine because I found that the 2.0 was far too slow through the gears compared to the Xsara which went like the wind. The 2.2 is quite nippy for such a large vehicle. I particularly like the different suspension heights and in fact used the highest one (max 6mph) to crawl through a flood yesterday. Also like the Sports setting which takes two of the suspension spheres out of commission thereby hardening up the suspension and reducing body roll on country roads as well as improving handling. I bought the vehicle at about 40000 miles (03) and in a year I have done 20000 miles. I have had it serviced twice at a local independent Citroen servicing centre and costs have been quite high. It seems to go through tyres as in that 20000 miles I have had to purchase 3, each about £60. Overall reliabaility is good but like numerous other 2.2 owners I have suffered, and still suffer from the phantom anti pollution sensor problem ie. the ESP Electronic Stability light comes on indicating a fault and immediately after another light (small engine shape) and words Service lit up. The display also indicates an 'anti pollution' fault and the ECU goes into limp home mode with only about 2500 rpm available in any gear. This first happened on the M25 with a caravan on the back - I kept going at 40mph until a rest area. Having switched off and left it for a couple of mins I switched back on and started up. The ESP light has gone out, revs are back but the anti pollution message persists - this goes out afet a couple of days and its back to square one. Computer diagnosis deoes not reveal the fault and it is not the Particulate Filter. This has now happened on numerous occasions to me and also to dozens of other people on the net. Noone seems to know the answer and it has spoiled what has been a super car for me and I will be trading in ASAP - what a pity. Overall MPG 40.3