In case anybody hasn't noticed, because of the disparate rates of increase, postage cost after the end of the month could actually
fall, if you have these current 1st or 2nd class stamps.
For example, 1st class large letters between 251g and 500g currently cost 146p, but 160p from May. So in May it can be posted for 2 current 2nd class stamps plus 1 current 1st class stamp, which currently cost 118p, a fall of 19% from today's price.
The reason price can actually fall using such stamps is because they will have appreciated far more in percentage terms than most other tariffs. It seems RM wanted to slap the biggest increases on the cheapest, most common services. The services school children and pensioners, orphans and widows use most. Great.
Health Warning: Am pointing subject out purely for amusement, no recommendation to sell your house raising money to buy stamps is either suggested or implied...
