Hi Hems, updated answer- most of what's below still stands (as you are asking for averages) so with the updated information the averages would be the same, however, I am assuming what you want in actuality is the specific 'predicted' estimate for these items, rather than the average for said items, as averages are given below on my previous answer.
If it is an estimate for said items, I'd charge half a day, and parking would be your responsibility to cover.
Some people would take another view on this but we are not they, and each company has differing requirements. You can look up our rates if required, we are in Winchester.
Certification for the install you describe would be a minor works certificate but is not legally required, although can be included with invoice upon completion at no extra cost
Hope this sorts you out.
Yours
DMELECTRICAL
Previous answer- this comes up a lot, and frustratingly many people base their answers on very limited assumptions, such as: they have installed mainly domestic simple single phase ovens, so the average time is based on this, when in reality, the world is deep, the world is high, and this is doubly so for the appliances you mention. So the following is, I feel, a better way to look at timescales, average or otherwise, and as I own my buisness this thinking reflects the charging required.
For each appliance in and of itself, there are different methods of installation, single phase two, or three phase: this is one parameter. For each appliance there are different versions (integrated (you kindly mention this), or stand alone), an additional parameter, for each appliance there may be different regulations for supply, yet again more perimeters, voltage, frequency? etc. Does the item come with a plug? A flex? Etc. All this needs to be known before a correct answer can be given.
For each appliance there are additionally different scopes required for an installation to be considered complete: simple things like unpacking the items, getting rid of rubbish, old items requiring moving or disposing of, all have an effect in the real world scenario of installation time.
For each parameter a direct effect on installation requirements and therefore time for installation (as you have asked specifically: 'How long it would take to install' for each of your three items).
Generally with simple direct, 'wiring in' alone with all cables already in place from the machine and terminations only, with all installation tools and equipment in place (crimps, ferrules etc) about 5 to 10 minutes to terminate. But this would not include fixing carcass in place, rubbish and so on.
From the viewpoint of the whole installation of each item, so what I term - 'in, on and rubbish away' or a whole installation , an hour to a day would be possible depending on what else is required.
Usually I install stand alone ovens in an hour, but I have at times worked on installations that require multiple visits to install equipment.
Best if the exact specifications of installation requirements are provided for an academic request such as this, plans, loads, dimensions model numbers, timeframes, etc.
None of this includes suitability of said items for their location with regard to load and safety requirements, as that is another realm of requirements.
So although it sounds like a large window, to give an average from my experience , I'd say the range is an hour to a day (not longer) if you average 'most' appliances, this could be termed maybe at half a day for the average? As it's either 1hour, half day or full day from a charging perspective.
Half a day average for all appliances of the general type you mention, but if you do the math, a chap who's fitted 100 regular beko stand alone cookers on a new build site might tell you 10 minutes because he is paid as an employee, but as an independent, with many more varied types of installation for 'cookers' it'd be closer to this answer at half a day, arga conversions put the overall average up too.
Hope this helps.
Have a good weekend.
Yours
DMELECTRICAL