Unless I’m missing something the 2020 changes won’t apply to any Morgans. The TfL website says
From 26 October 2020 the LEZ emission standards for heavy vehicles will also set a limit for emissions of nitrogen oxides (NOx), which form harmful nitrogen dioxide (NO2) in the atmosphere. Vehicles need to meet the LEZ emissions standards based on vehicle type and the type of emission.
From 26 October 2020, LEZ standards will be:
Euro VI for buses and coaches over 5 tonnes, lorries and other specialist vehicles over 3.5 tonnes - this is the same as the ULEZ standard (these vehicles will no longer need to pay a separate ULEZ charge)
Euro 3 for PM for larger vans and minibuses - this is the same as the current LEZ standard
If you drive a larger van or minibus within the ULEZ area, you also need to pay the ULEZ charge if you do not meet the ULEZ standard of Euro 4 petrol/Euro 6 diesel.