You don’t need an electric van to avoid the ULEZ, it just needs to be Euro 6.
(Almost all vans that you put AdBlue in are Euro 6)
I’ve considered getting an electric van for my next one, but at the moment they are too expensive. Even when you account for not paying diesel the 5-year cost is still higher, (plus they’re less convenient. Charging taking hours rather than a few minutes to fill)
At least that’s how it was when I last looked a few months ago. Maybe things have moved on?