Ok so looks like the last one for a while and got the lowest mpg:
Trip 6 NE- Cornwall, Tesco 68.9mpg, Average | 51mph Average (66.5mph cruising) 1pm start, heavy traffic 14-19deg c, mostly light rain.
I think my higher speed (in a rush) and the rain made the impact, trip 5 on the way up was void as I had a very different route and was also behind schedule so sat on the M6 at 2800rpm **mph, so that’s it for the back to back similar trips for this year, I didn’t get as many in as I thought and for me the data didn’t really show any worthwhile expense in splashing out on premium fuel in terms of an efficiency improvement and if your not get any more efficiency I doubt there’s any extra performance either, so it would be just down to detergents. For me there are two cheaper options for that either flush out with veg oil prior to a filter change or add a specific fuel system cleaner once a year as part of your preventative maintenance, just my thoughts yours welcome also.