Siting of compost bins...

I wouldn't put it in the middle of the bed.  It will create shade and I don't think the beneficial area will spread out far from the actual bin (I moved mine some years ago and the area it had been was clearly defined by the height of the spuds the following year!).

Any weeds that spread out will only compete with your crops and potentially be difficult to remove.

I'd keep it out of the way at the side and maximise your growing potential / flexibility on the bed.

You need a workable area around the bin for getting the barrow in and out for filling and emptying purposes so the middle of the bed is a poor idea. You can have an area in the centre of the plot just for the bins as they do like full sun, and if you have enough room, why not. Mine are lined up on the edges of my plot in the hedge bottom but they do get plenty of sun

I suppose so but frankly, given the height of bins, then anywhere round the edge would be fine as it's unlikely to have a significant impact on nearby beds or neighbours' plots whereas a shed is a much bigger proposition.

The question related to growing plants in the immediate vicinity.

then again -

If you know you won't want access to the compost until say autumn at the end of the growing season or early spring before sowing/planting, you could potentially put your compost bin in the middle of the plot and grow something like Butternbut Squash or Pumpkin at the base of your bin and it would benefit from any run off and possibly even scramble over the bin as a framework. any weeds would then be suppressed by the vines.

I don't think I would do it though as I need access to and from my compost through the year. I just like to entertain the opposite side of an argument as I think it is healthy to do so.