There are other posts here dealing with this problem in various efficient ways. This project was initially tackled in yet another different way. The problem is a common one where both depression and rotation of the control is required. A removable operator was designed that could be slotted into the aperture of the stove. The constituent parts of the device are cheap easily available hex drive accessories for screwdrivers. The three pictures show the principle quite clearly.
In practice although the device was successful, this was not a good solution for this client as the positioning of the operator proved too difficult. The idea is detailed here as it may be applicable for others.
The final solution was another variant on the universal joint concept. In this case the control knob was replaced by a brass bar, providing a suitable receptacle for a forked operating device at the end of a long steel bar.
Bedfordshire North Panel BN25/14