Driven down to Heathrow today and the AVG MPG indication was stuck on 27.2 for around 90 miles and would not change however hard or soft i pushed the throttle, only changed back to avg reading once i reset via the stalk, is this a fault and if so has anybody seen it before or know the fix (other than pressing reset) or do i add it to the long list of problems that will be presented to the dealer on Friday Am i just having a bad experience or is reliability on the RRS an issue that i was not aware of prior to purchase, i have had more problems in the 3 weeks of ownership than i ever had in 6 years with Lexus?

Leeds it sounds to me like you may not have reset the trip and the mpg when you filled up?
If you don't press and hold in the "i" button on the end of the left hand stalk until you get a row of dashes then you haven't reset the system, to reset the trip miles either press the black button in the instrument cowl or scroll the info screen to trip and then hold the button in until it has zeroed, but you must reset both to get the average mpg to change. After reset the figures will change quite frequently until you have covered 5-10 miles and then steady up. The fact that you drove 90 miles and it didn't change means one of two things - you either have never reset the trip compouter or you drive with an amazing resistance to have the odd burn up enroute. Yesterday when I drove mine from Southampton to Stirling (480 miles) the trip changed rapidly and then steadied out at 32/33 mpg depending on how I drove - speeds at anywhere between 70 and 110, what made the big difference to my consumption was 10 miles of roadworks with 50mph average speed cameras every 1/2 mile in Lancashire on the M6

The reset method for the average mpg and trip are in the owners manual..................................... 2020 Pangea Green 1st Edition D240 New Defender 110 is here and loving it
2018 Melting Silver Mini Countryman PHEV - soon to be replaced
2015MY Corris Grey SDv6 HSE Dynamic, the best car I have ever owned, totally reliable only a cou0le of rattles in 3 years, now no longer in my care
Also in my garage is a 1996 TDi300 Defender 90 County HT made into a fake CSW

Yes looked in the manual first but not what i am experiencing, filled up yesterday and was working fine set of this morning and all fine fluctuating as you would expect around country roads get on motorway and again working fine until around 30 miles into journey then just stuck at 27.2, gunned it from 50 to 100 to try and influence a change but still no fluctuation. Stayed on 27.2 for around 90 miles then i pressed button at end of stalk for 2 or 3 seconds and it reset and started to work correctly, it was as if it had just frozen for the 90 mile period.

Wonder what the dealer can do for it then other than reset it again when they try pressing the buttons! 2020 Pangea Green 1st Edition D240 New Defender 110 is here and loving it
2018 Melting Silver Mini Countryman PHEV - soon to be replaced
2015MY Corris Grey SDv6 HSE Dynamic, the best car I have ever owned, totally reliable only a cou0le of rattles in 3 years, now no longer in my care
Also in my garage is a 1996 TDi300 Defender 90 County HT made into a fake CSW

My central screen froze and wouldn't react much in the way you described. The dealer found a fault/glitch with the software and reinstalled it. Other than this one minor event the car has been flawless over the past 12 months and 27000km.