I'm happy to take the hit on discretionary income because I know that it is a bill that will not rise much in the next few years. On the other hand interest rates will continue to increase.
However, the primary reason for selling is simply I don't want to be stuck where I am now. It's not somewhere I'd ever want to bring up kids (though such an event is probably a good few years away) so I'd prefer not to be stuck living here unable to sell because the market has tanked. It is the FTB market that will take disproportionately large hit when the market does actually collapse.
Also, I could if I wished simply park the gain in a bank and pay rent for about five or six years from it. I won't be doing that but it will be reassuring to have it there just in case. I'm expecting a substantial salary jump in the next year or so too, so that should definitely put me in a position to comfortably afford to rent a property I could never afford to buy.
I shall be happy to post here letting people know how I get on.