yeah i always fancied The Right Reverend Brigadier Sir...but upon doing further research felt that joining the clergy and working my way up to bishop whilst simultaneously joining the army and working my way up to Brigadier might be somewhat difficult. Seriously, you're joking right?
You can buy titles - not that I agree with that. Try doing a Google. But you can also just change your name by deed poll. This is ok as long as you are not doing it for criminal (e.g. fraudulent) purposes. Of course, you'll lose all the respect of your friends and don't think that HMQ is going to start inviting you round for tea.
A friend of mine bought a knighthood from some twerp in Australia. Then he bought/earned a Doctor of Divinity degree from some weird church in the US. Now he calls himself "The Reverend Doctor Sir B**** S********". He's seriously lost the plot and so has anyone else who goes round buying titles he can't even spell. You are being pretentious to the nth degree and everyone can see it.