So, in the end I went for a 2017 MINI Cooper SD (Chilli Pack)
8 months old, with 1300 miles, 1 owner - BMW Employee Benefit Scheme.
With cruise control on the motorway, it's averaging 51mpg and i'm filling up every 11-12 days rather than every 5-6 in the Celica - so looks like i'm saving around £80/month in fuel, tax is just under half the Celica, insurance about the same, and with BMW Recovery included I can cancel my RAC membership.
Performance wise it uses the BMW B47 2.0 TwinPower diesel lump delivering 170bhp and 0-60 in 7.2 secs, very different power delivery to the Celica and much better on the motorway, the driving modes make a big difference too.
It's a Mk3 MINI and the first one that is BMW from the ground up, not 3rd party engines or parts, and to be honest it feels like a BMW inside, very similar trim and switch-gear etc to the 1-series I had years ago. Equipment wise the Chilli Pack makes all the difference, giving bigger wheels, driving modes, boot floor panel, cruise control, LED headlights/fogs/main. But being a BMW it's amazing what isn't included for this spec in this day/age - SatNAV, reversing sensors, keyless entry (but keyless start is ?).
My wife also got a new car around the same time - a Nissan Juke, and interesting to have the realisation that we bought new cars - one German, one Japanese, and they're both made in the UK.