We went for the packet post thing & didnt find it was any use at all, rtaher complicated, no tracking feature and we had to lug it all to our local post office.
They do pick up but charge a fee per month which kills any savings you make unless your doing big numbers.
There are many couriers out there really fighting for business at the moment.
We have also just discovered that Fastway will deliver anything that will go into their large 5kg bag for 3.95 + vat & they now give you 30 days to pay for the tickets.
This only applies to their covered areas which is about 80% of the country.
The best tip I cna give you is to ask all the couriers for a quote, over estimate what you would be sending to get better rates.
Don't take thier first offer as they will come back with a cheaper price after a few weeks & they are all very hungry for business.
You have to factor in that certain areas such as highlands & islands are alot higher with some firms, although dhl have just offered to do them for £6.00 which is better than our current rate of £12.00 per delivery.
hope that helps
G