Odd but this question has been asked on another forum when the oven supplier refused to connect them up.
I motor needs a local isolator, but an oven or hob does not, the isolator could be anywhere including with a TN supply using the MCB or RCBO.
All it needs is a method to lock it off.
However most ovens and hobs have around 1.5 meters of flex which needs connecting to the supply, so you do need a cooker connection unit to actually change from fixed house wiring to flexible cable going to oven or hob.
As to size of supply, I would say 32A is normal and having one 32A supply for both is OK, however 45A is not normal and I would not directly connect a 45A supply to an oven, unless the manufacture says it is permitted.
Clearly two 16A supplies is best option, but that is not normally done, you can get double cooker connection units designed to connect two cables into the supply, I would use one of them.
If the ovens are British and 3 kW or less I would use two fuse connection units, if using non British and it is over 3 kW then just use a double cooker connection unit.
Personally I would use a 45A isolator on the wall so you can local isolate so there are no problems in the future if you want a supplier to connect up a new oven, as they often want to be able to see the isolator, but it is not required, just good practice.
Reason for cooker connection unit is to have some where to connect the oven within 1.5 meters of the oven, other wise some cooker supply people will not connect it.
Does not really matter if a dedicated cooker connection unit, or a switch but some thing within 1.5 meters of the oven or cooker.
In this case two ovens so between them it would need a 32A supply, so a cooker isolation switch would be required for that current. I know you can get a light switch rated 20A but I would not be happy with 20A switch on a 32A supply.
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