I live in a bungalow and wish to remove the immersion and tank to make the bathroom bigger, looking to replace the immersion with something suitable to feed 3 basins, kitchen and two vanities, i have been told two separate systems, non vented cylinder in the loft or a instantaneous heater supplying all 3 sinks, 2 plumbers disagree and i am now confused!

You don't mention baths, showers etc.

I would look at instantaneous gas fire water heaters, or if you're talking all electric a small unvented cylinder.

The electrics could be a problem with have an instant water heater to all 3 basins.

I think a small unvented cylinder with a double immersion heater, so you could run it with E7 over night.