That's Tesko territory... LOL! What are we looking at... the blue and white coat hung on the wall to the right of the AGA?
A photo of the kitchen after clean-up showing light bulb without lampshade. If any broken pieces of glass were left attached to the threaded fastener of the light bulb socket, then it looks like they've been removed...

I've no idea what the Mythical Tesko has or hasn't said, sorry. But thanks for posting this photo, which confirms there is a central light in the middle of the room, midway across the Aga, because that's where the dark blue thing is in the other picture which must indeed be the lampshade. I deduce from its shininess and the fact it's still there that it is made of plastic not glass and that if the kitchen light was on when the police arrived means the bulb was also not broken. I'd also be surprised, if Bamber was the murderer, that he would point it out as he did.
So it's not so surprising that Sheila would not have broken glass or blood on her bare feet.