Hi @Jan_B,
Thank you for your question about removing taps to change their washers.
Also, a warm welcome to the Bunnings Workshop community, it is wonderful to have you join us.
This is an educated guess as I'm not aware of these specific taps, but the H and C buttons on the tap are likely removable.
I'd suggest these can be levered off with the use of a small flathead screwdriver to reveal the inner mechanism of the tap.
Once revealed, you might like to have a look at How to replace a tap washer for some guidance on the process.
Let me know how you go, if this is not the solution, I am more than happy to help further.
Jacob
Hoping someone can tell me how to remove these to change the washers...cant find any reference to them online at all. Help! 
