2011 Royal Mail tariff: April/May price increases

Royal Mail have announced their price changes for this year. There are two different price changes, one tariff for stamps and franking (opens in .pdf) customers which comes into effect on the 4th April 2011 and another tariff for account customers (opens in .pdf)which will be introduced on the 9th May 2011.
The cost of a basic 1st class stamp will rise for those buying stamps from 41p to 46p, a 12% price increase. As a seller on eBay you’ll need to check the prices for the service and weights of the products you sell, but expect the cost of posting a 251-500g packet to rise from £2.24 to £2.48 a 10.7% price rise.

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If you’re a Royal Mail account customer you’ll also need to check the new rates to determine the rise in postage costs that you’ll be charged, although they won’t change until May.
As an example we’ve checked the costs for Packetpost, for which charges are based on the average weight and format of all the parcels you post. For low weight items the price increases are as steep as 15% for both first and second class post, although if your average weight is higher then the percentage increase drops to around 5%.
Which ever method of posting you use the price increase is bound to be unwelcome, but compared to courier Royal Mail is still the most cost effective method of delivering low weight items within the UK.
Which postage services do you use and how will the price increases affect your business? Are the price rises high enough to make couriers attractive for your products or will you stick with Royal Mail?