Replacing 'main' ignition switch on Bosch gas hob

[KateMoss]

Hello, I have a Bosch gas hob with a small, spring-loaded 'main' push button switch which needs to be depressed before any of the burners will light. This hob was not bought by me and the id. numbers are impossible to read correctly without dismantling the kitchen unit - I am not that desperate yet! It says Flametronic on the top. Yesterday the push button popped out while my back was turned and it looks as if it is just a plastic rod about 20 mm long which has snapped near the far end i.e. the end away from the bit you actually push. It looks like there is another little bit of it stuck further inside the switch casing. A little spring popped out too. OK, this is all a bit tricky without pics but unfortunately I'm not able to supply any at the mo. I am wondering if anyone can recognise this scenario and advise if the whole switch is possibly replaceable - I am hoping the (cylindrical plastic) switch housing can just be prised off the top and a new one would fit onto some contacts. The appliance is of unknown age but I suspect it is not a very recent model. Thanks for reading.....

 

[KateMoss]

For info: Actually managed to find the model - NHT645SGB/01 FD8304 and the part appears to be 00609162 as on
http://www.applegate.co.uk/b2b-products-services/9f5052508e8611e395ed005056822514.html

Looks like it is secured to hob top by a nut underneath. Any ideas on possibility/degree of difficulty replacing this without need for gas engineer?