I've let you ramble on to permit you to debunk your own case.
The knobs, Joe, the knobs. I assume they're Bakelite; extemely poor heat conductor and used for a reason - they don't get hot, otherwise the user would burn their hands every time they touched them.
Can anyone think of something that would be hot enough to superficially burn skin in that kitchen during the attack?
....and you still haven't explained how 7st 6lb Bambi managed to subdue the farm-fit 15st Nevill.
I can tell you a little bit about Aga's as we have one exactly the same model as the Bamber's. The only difference is that theirs was used to heat water. Their kitchen, like ours, appears fairly cramped. Aga's throw out vast amounts of heat. Ours runs 24/7 because it's out primary cooking method. The Bamber's had alternative means of cooking, ergo, it seems reasonable that during summer months, the Aga would be turned off and an emersion heater used to provide hot water.
So how hot do Aga's get? I don't imagine you need to be told that it's not a good idea to put one's hands on the hot plates, even though one is less hot than the other. The hot plate covers are hot enough to air small items of clothes. However, Boyce and his crew weren't dealing with the top, they were dealing with the oven, of which there are two, a roasting oven at the top and a slow oven at the bottom. I can open the slow oven door without oven gloves, and providing the handles of the dish aren't metal, I can remove a cooked item without them. Under no circumstances could I touch the handle of the roasting oven without protection.
The various knobs/handles to which Boyce refers to as having made burns? I have measured ours numerous times. It's not just about the distance from one handle to another. They not only vary in shape, but they also stand proud of another. The 'body' Boyce uses for his experiment is, obviously! very much alive so thus is able to 'adjust' himself to fit against the handles. Something Nevill wouldn't have been capable of doing. My calculations -for what they're worth- show the distance between handles doesn't relate to the distance shown on the pigskin experiment, and burning would only apply if the Aga was hot.
I hope this is useful.