To get at the base element on these you need to pull the oven out from the unit.
Open both doors and look on the side as theres usually screws holding the oven to the unit.
Remove them and then you can pull the oven out and onto the floor.
Once out make sure the power is turned off and then you need to remove the back panel.
From there you will see you will see the wire going to the elements. The base element will be at the very bottom and lift the insulation up which you will see and you can then see the screws that hold it in place. So undo the screws and then you can pull the base element out from the back and swap it over.
So to fit this is all done from the back im afraid. If you need anymore info just get back to me.
No worries that's fine. Just let me know how it went.
All done, thanks for the help. It is a right fiddly job and I will have itchy hands from the insulation for a few days, but at least now we can bake again.
Nice one glad to hear you sorted it and thanks for letting me know how it went.