This is standard practice. MPs receive a lot of letters from their constituents and it isn't practical to send individual responses.

As well, Amber Rudd and Damien Green are conservative MPs, so they can be considered supporters of this proposal. I would hardly expect their replies to do anything other than make positive statements about the proposal.

There's more to democracy than voting and writing to MPs. For example, in light of the leaks about GCHQ and this proposed internet censorship, I have started supporting Pirate Party UK. They are the only party with a satisfactorily strong anti-surveillance and anti-censorship stance. Put your money where your mouth is.