It's a good question.
I wanted to comment on Kevin's very good answer but I am not yet allowed to do that.
My understanding is that the Speaker is elected as an MP unchallenged in their constituency, by convention. So the other main parties do not stand candidates against the Speaker in any general election. This makes sense, because the Speaker does not act as a normal MP in the House with regard to voting etc, so there is no need to count them as an MP to be defeated in the parliamentary arithmetic. Their existence is "baked in" to (or out of) any calculations about majority etc. I do always think it is a bit odd that if you are a (say) Labour supporter in Buckingham, you are pretty much disenfranchised for as long as Bercow is Speaker. But that's the system we have.
I am no sure what the situation is with the deputy Speakers in the HoC. I imagine they act more like normal members regarding voting etc but I'm not sure.
I don't suppose that the Speaker has much time for dealing with normal constituency matters - they will employ staff to handle that sort of thing on their behalf. The same as it is with ministers of State who I guess rarely if ever do actual constituency work and surgeries - they don't have time. Tony Blair had a guy, a close friend of his I believe, in his Sedgefield constituency (a long way from London!) who IIRC did the vast majority of the Sedgefield standard MP stuff on his behalf.