I have just completed the first reasonably long drive in my Vectra SRi CDTi (150), a 551 mile round trip from home to Galway in the Republic of Ireland. I was slightly disappointed by the fuel economy, I averaged 56.5 mpg on the trip to Galway, but for some reason did quite a lot less well on the trip back, ending up with an average of 52.3 mpg for the complete trip. While these figures are much better than the 42 mpg I average with normal use, I had hoped to get closer to 60mpg on this journey. I also have to say that despite the majority on here loving the SRi seats, while I no longer have a problem on my daily commute, after this longer journey I really was very soar and fatigued with the SRi seats in comparison with how I was on my significantly longer drives in my Mondeo on my Summer holiday to Cornwall.
In the end, I used the Irish toll M-ways. Great roads, more equivalent to a UK dual carriageway in that they are 2+2 rather than 3+3, but partly due to the low population density and party due I think to the locals being reluctant to pay tolls, the roads were very empty. I was able to cruise at 120km/h for the whole length of the M1, M4 and M6 and at the legal 100km/hr on the M50 (Dublin by pass). The brand new service areas that I stopped in (M1 south, and M4 East) were nice but again deserted with far more staff than customers. Hard to see how either the services or manning the toll booths could be profitable - still the emptiness of the roads is a revelation compared with driving even on the M-ways in Northern Ireland, never mind in over crowded England.