How easy is it to replace the simmerstats on my Belling E665?

Two of the simmerstats on my Belling E665 seem to have failed simultaneously It is a ceramic hob cooker and one of the two simmerstats controls the halogen plate. Also, the fan which cools the hob (NOT the oven) has started to make a strange noise for the first five minutes of operation.Seems to be OK when the cooker has warmed up fully. It would be expedient to replace all three failed parts at the same time. I was a trained (aircraft) electrician and usually feel comfortable with domestic appliance repair.