Back from our week away and with time to think she's now set on having an FR. Which engine version is yet to be decided by what we can find out there. We've yet to have a test drive in a 1.4 but look forward to doing so soon.
Is there such a thing as a diesel FR that's not a 2.0?
Sadly no, all FRs are at least 140PS powerful. The least powerful engine in their line up is 'tada' the petrol 1.4 140 PS for that era. The 2017 models have a 1.4 125PS FR. Weakest Diesel is the 2.0 TDI 150.
50mph flat road, should easily get you low to mid-50s. I do a not dissimilar journey once a week, 16 miles, 50mph zones...car would give (note I have a 1.0 TSI though) anywhere between 56-62mpg with very light traffic.
If you can find a petrol 1.4 ACT 150 within your budget, that woudl be the one to go for. One forum member recently got 64mpg over 200 miles with average speed of just over 50mph. That's diesel territory...