given the choice i would also increase the depth of the base cabinets but depends on layout of the whole kitchen and available space

Thanks @oklouise, unfortunately we don't have much space to increase the base cabinets.

then i suggest you test the depth with any cabinet where you live now because 420 is almost half as deep again from the standard wall cabinets ...measure the size of what you will store in the cabinets and then reconsider the lights...there are other lighting options and the deeper wall cabinets will add substantially to your costs if you don't need the space and it might also create problems for installing a range hood

Our kitchen people are happy to increase the depth of the top cabinets without any extra costs. I'm just worried whether this is practical and was wondering if anyone has installed deeper wall cabinets?

What type of range hood are you using, 300 is the norm for wall cabinets. base 600, this allows for best use of the counter top sinks and cook tops

It's an under cupboard rangehood which is already 300mm deep. The only appliance on this wall will be the rangehood and cooktop, no sink.

Basically it will restrict your head from the overhead view by 12, I'd find a lighting system that will work with the 300 wall cabinets or just go with that, there will be slightly more cabinet material to be covered cost wise

420mm deep is common for wall cabinets as stronger range hoods are usually deeper. Sometimes to add LED light. We do it often. No issue. Most canopy range hoods are 450mm deep.

420 looks very deep. It will create issues in terms of use and application.

Deep cabinets get mounted higher so you don’t hit your head when using bench and can see to wall. Being deep it is easy to loose things at back of cupboards as hard to reach in

My led strip in my laundry cabinet is in a 2.5cm channel set into a false base. Basically a second base piece cut to accommodate the channel, but I guess it depends on what the light strip is?

Mounting wall cabinets higher, looks OK but restricts use of the cabinet by being unable to reach things without using steps. I would checkout Dr Retros experiences and a good lighting supplier. I remember using this style of light; mounting them up under the the wall cabinet and against the splash back, a small matching strip/beading of cabinet material is placed on the outer side of the strip light to what ever suits your taste

Thanks everyone, they now said it can be reduced to 390mm instead of 420mm. The type of channels they recommend are these ones.