Torque Converter lock up in cold weather

[Unaz]

Hi everyone,

We bought a 2009 Toyota verso 1.8 valvematic (CVT) few months ago after ulez became a problem for our diesel.

I've noticed Torque converter locks up at around 25mph when engine/ transmission fluid is cold and around 10mph once oil is warmed up.

In warmer weather that happened pretty quickly but now that it's getting cooler it's taking forever to warm up and therefore most of our driving (short trips of less than a mile) is done with torque converter clutch open. It's returning around 18mpg and feels very slow to move off the line, revving quite high for acceleration.

Car drives absolutely fine otherwise and has returned 40 mpg on 400 mile trip of mixed driving (mostly motorway) in August. 

CVT oil has been changed few months ago which made some noticeable difference.

I was wondering if there was ECU update to lock up torque converter earlier as later models have reduced Co2 emissions which might possibly be to do with early torque converter lock up?

Anyone able to check if there's an update available for my car and if Torque converter does lockup early on newer models?

Appreciate any advice/ help. 

Current Engine and Ect software calibration I.D. is 30F21100  A0C01000

VIN NUMBER NMTDG26R60R013250