Why on earth is this country so expensive?

I went into a corner shop in Pimlico to buy a single 1st class stamp. Admittedly its been a while since I bought my last one, I think it cost 29p last time, today it was 80p. 80p! But where have you hidden your horse Mr Turpin?

A first class stamp is 60p. A 20p service charge is a bit steep.