I would guess the huge price hikes are something to do with the government budget cuts, requiring Royal Mail to operate at a greater profit to help pay for hospitals, schools, ministerial limousines etc.
The definition things are a bloody nuisance, but I think one or two of the things said above aren't quite right, e.g.,
These should still be able to go as Medium Parcel rather than Parcelforce - it says "Roll or cylinder shaped parcels larger than these sizes can be posted as Medium Parcels up to and including 90cm in length and up to and including 104cm (length plus twice the diameter)"
Having to wait in for a Parcelforce collection
Parcelforce are in fact encouraging you to leave your parcel at your local post office for collection, and that way you get a £1 discount. There is a further £1 discount if your buyer will collect the parcel from his local post office.
This always could be a problem, depending on whether the post office took the rules literally. Does a 61 x 61 x 3cm package come within a 61 x 45 x 45cm limit? Strictly speaking no, but its volume is about a tenth of the volume of the biggest medium parcel, so common sense has often prevailed in the past. It depends whether the local post office wants to turn away business. Maybe they'll be forced to in future.
Again it depends on how literally they take the limit - 70 x 20 x 10cm is about a tenth of the volume of the biggest medium parcel, so we'll see. Anyway, even if it was accepted as a medium parcel, the price for that kind of weight has gone up hugely, so not all that much different to a Parcelforce price.
I like the sound of myHermes and I think I'll give that a go. The max length of 1.2m and max weight of 15kg could be a problem for sending bikes, but I think 1.2m isn't a lot different from Parcelforce's 3m for length plus girth (I usually go for 120 x 70 x20)
Common sense is not very common at post office counters. It does exist, but only in isolated pockets...
Give a man a gun, and he can rob a bank.
Give a man a bank, and he can rob everybody.